Javascript 中“call”的使用 红太狼 2022-08-06 14:14 136阅读 0赞 <table style="word-wrap:break-word; empty-cells:show; border-collapse:collapse; table-layout:fixed; width:757px; color:rgb(68,68,68); font-family:微软雅黑,Tahoma,Helvetica,SimSun,sans-serif; font-size:12px; line-height:18px"> <tbody style="word-wrap:break-word"> <tr style="word-wrap:break-word"> <td style="word-wrap:break-word; font-size:14px"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">Javascript中call的使用自己感觉蛮纠结的，根据文档很好理解，其实很难确定你是否真正的理解。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">call 方法</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><a href="http://www.html5cn.org/portal.php?mod=list&catid=20" style="word-wrap:break-word; color:rgb(51,102,153); border-bottom-width:1px; border-bottom-style:solid; border-bottom-color:blue" rel="nofollow">应用</a>于：Function 对象</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">调用一个对象的一个方法，以另一个对象替换当前对象。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">call([thisObj[,arg1[, arg2[, [,.argN]]]]])</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">参数：</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">thisObj </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">可选项。将被用作当前对象的对象。 </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">arg1, arg2, , argN </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">可选项。将被传递方法参数序列。 </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">说明：</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">call 方法可以用来代替另一个对象调用一个方法。call 方法可将一个函数的对象上下文从初始的上下文改变为由 thisObj 指定的新对象。如果没有提供 thisObj 参数，那么 Global 对象被用作 thisObj。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">1.最基本的理解：示例1</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">自定义一个类，该类有一个方法showTxt，用来显示当前对象的name值。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">创建一个对象，并且该对象的name值等于test1。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">使用call方法，使新创建的对象obj添加Class1类的showTxt方法，即把Class1类中的this.showTxt中的this指定成obj，这样obj就有了showTxt方法。弹出"test1"。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var obj = new Object();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> obj.name="test1"<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class1.call(obj);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> obj.showTxt();//test1<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(obj.showTxt);//function(){alert(this.name)}</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">这个例子很容易理解。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">2.再看一个稍微深入的理解</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例2：创建Class1的实例，让这个实例调用showTxt方法返回这个实例的name值，因为这个实现没有name值所以返回undefine.</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class1 = new Class1();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class1.showTxt();//undefined<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(class1.showTxt);//function(){alert(this.name)}</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例3：下面就给Class1添加个name值，这时class1再调用showTxt方法，会返回class1，这是因为给类添加了name值，所以实例的name也由undefine变成了class1.</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class1';//添加name值<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class1 = new Class1();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class1.showTxt();//class1<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(class1.showTxt);//function(){alert(this.name)}</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例4：Class1.call(obj) 这个操作把Class1中的this.name,this.showTxt里的this替换成了obj，所以就变成了obj.name='class1'，所以obj.showTxt在执行时返回class1。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class1';//添加name值<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class2';<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class2 = new Class2();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class1.call(class2);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(class2.showTxt);//function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class2.showTxt();//class1</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例5：如果在Class1.call(obj);之后再添加obj.name = 'test1',最后结果会输入test1，原因显而易见。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class1';//添加name值<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class2';<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class2 = new Class2();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class1.call(class2);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class2.name = 'test1';//重定义obj.name值<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(class2.showTxt);//function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class2.showTxt();//test1</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">上面的例子call的都是一个对象的实例，接下来的案例把对象的实例直接换成函数，看看执行结果会发生哪些变化</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">3.把call方法的第一参数由实例换成函数看看会怎么</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例6：Class2是一个function对象的引用,在执行Class1.call(Class2)时this.showTxt里的this被替换成了Class2。这样Class2就有了showTxt方法，Class2.showTxt()执行时会返回Class2.name的值，因为Class2并未定义name值，所以会返回undefined。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">Class2函数里的this.name是由Class2创建实例的name值，并不是Class2.name，这两个值有时会让我迷糊。</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class2';<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class1.call(Class2);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(Class2.showTxt);//function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class2.showTxt();//undefined</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">4.接着看下面的例子</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例7：class1.showTxt.call(class2);之所以会返回class2是因为function(){alert(this.name)}这里的this被call指定成了class2，变成了alert(class2.name)，所以会返回class2.</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">alert(class2.showTxt)返回undefined，说明并未定义class2.showTxt方法。</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class2';<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class1 = new Class1();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class2 = new Class2();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class1.showTxt.call(class2);//class2<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(class2.showTxt);//undefined</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">因为并为给class2添加showTxt方法，所以提示该错误。如果在这个调用之前添加Class1.call(class2);这个调用就OK了</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Class1.call(class2);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class2.showTxt();//class1</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例8：这个例子都会返回undefined</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.showTxt = function(){alert(this.name)}<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function Class2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> this.name = 'class2';<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var class1 = new Class1();<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> class1.showTxt.call(Class2);//undefined<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(Class2.showTxt);//undefined</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">5.在使用call时如果调用函数里没有this会怎么样</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例9：</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function add(a,b){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(a+b);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function sub(a,b){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(a-b);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> add.call(sub,3,1);//4</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">结果返回4，add.call(sub,3,1)在执行过程中，sub做为add函数中this的替代品出现，但是因为add里没有用到this，所以sub函数直接忽略，所以结果是4。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">所以实际执行如下：返回4。</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function add(a,b){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(a+b);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> add(3,1);//4</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">6.不错，接下来再理解一个怪异的形式</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例10：</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(1);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(2)<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var f3 = f1.call;<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f1.call(f2);//1<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f3.call(f2);//2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">f1.call(f2);比较好理解，如果不理解看上边的case，但如何理解f3.call(f2)会返回2呢，为了方便理解进行一下等效变化为f1.call.call(f2)，这时会发现实际上是f1.call方法call调用了f2，那f1怎么又会有call方法呢？call, apply都属于Function.prototype的一个方法,它是JavaScript引擎内在实现的,因为属于Function.prototype,所以每个Function对象实例,也就是每个方法都有call, apply属性。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">在理解f1.call.call(f2)时我们首先要知道call方法到底是如何执行的，这样才能f1.call.call(f2)如何执行。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">示例11：</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">引用JK写的一个用apply实现call的方法：</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function jsCall(oThis){//这里的jsCall就是Call<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var argsNew = [];<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> for(var i=1;i<arguments.length;i++){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> argsNew.push(arguments[i]);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> return this.apply(oThis,argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Function.prototype.jsCall = jsCall;</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">或简写成</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function jsCall(oThis){//这里的jsCall就是Call<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var argsNew = [].slice.call(arguments,1) <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> return this.apply(oThis,argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Function.prototype.jsCall = jsCall;</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">这样就得到了一个和call一样功能的jsCall.</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">接下来构建两个函数f1,f2</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f1']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f1(11);//[object Window],11,f1<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f2']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f2(22);//[object Window],11,f2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">用jsCall把f1中的this替换成f2</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f1']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f2']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f1.jsCall(f2,11);//function f2(a){alert([this, a, "f2"]);},11,f1</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">执行结果发现[object Window]被替换成f2函数</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function jsCall(oThis){//这里的jsCall就是Call<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var argsNew = [].slice.call(arguments,1) <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> return this.apply(oThis,argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Function.prototype.jsCall = jsCall;<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f1']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f2']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f1.jsCall.jsCall(f2,11);//11,,f2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">在执行f1.jsCall.jsCall(f2,11);时返回11,,f2，为什么会返回这个结果，重点来了<img src="http://bbs.html5cn.org/static/image/smiley/default/smile.gif" alt="" style="word-wrap:break-word"></span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">f1.jsCall方法：</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(f1.jsCall);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> //返回<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> //function jsCall(oThis) { <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> // var argsNew = [].slice.call(arguments, 1);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> // return this.apply(oThis, argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> //}</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">所以f1.jsCall.jsCall可以替换成jsCall.jsCall看一下执行结果</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function jsCall(oThis){//这里的jsCall就是Call<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var argsNew = [].slice.call(arguments,1) <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> return this.apply(oThis,argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Function.prototype.jsCall = jsCall;<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f1']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f2']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> jsCall.jsCall(f2,11);//11,,f2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">接着分析</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">jsCall在执行的过程中，return this.apply(oThis,argsNew);里的this被替换成了f2，11做为参数传给了(oThis,argsNew)，变成了f2.apply(11);</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function jsCall(oThis){//这里的jsCall就是Call<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var argsNew = [].slice.call(arguments,1) <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> return this.apply(oThis,argsNew);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> Function.prototype.jsCall = jsCall;<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f1']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(a){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert([this,a,'f2']);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f2.apply(11);//11,,f2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">返回结果跟f1.jsCall.jsCall(f2,11)一样。</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">回过头来看</span></span><br style="word-wrap:break-word"> <br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f1(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(1);<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> function f2(){ <br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> alert(2)<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> }<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> var f3 = f1.call;<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f1.call(f2);//1<br style="word-wrap:break-word"> </li> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f3.call(f2);//2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">这样就不难理解f1.call.call(f2)实现时，f1.call执行过程中call中的this被f2替换成了f2.call();因为f2里没有this的引用所以执行结果是2.</span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <div style="word-wrap:break-word; overflow:hidden; margin:10px 0px; padding:10px 0px 5px 10px; color:rgb(102,102,102); zoom:1; border:1px solid rgb(204,204,204)"> <div style="word-wrap:break-word"> <ol style="word-wrap:break-word; margin:0px 0px 0px 10px!important; padding:0px!important"> <li style="word-wrap:break-word; margin:0px 0px 0px 2em; padding:0px 0px 0px 10px; list-style-type:decimal-leading-zero; font-family:Monaco,Consolas,'"Lucida Console"','"Courier New"',serif; font-size:12px; line-height:1.8em"> f2.call()//2</li> </ol> </div> <span style="word-wrap:break-word; margin-left:43px; font-size:12px; color:rgb(51,102,153)!important">复制代码</span> </div> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word"><br style="word-wrap:break-word"> </span></span><br style="word-wrap:break-word"> <span style="font-family:微软雅黑; word-wrap:break-word"><span style="font-size:14px; word-wrap:break-word">需要十分注意的是f1.call是方法，f1是函数对象，这两者在call时是有区别的。</span></span><br style="word-wrap:break-word"> </td> </tr> </tbody> </table>
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