ES6标准入门（第二版）----读书笔记

痛定思痛。 2021-09-20 10:10 254阅读 0赞

<!DOCTYPE html>
    <html>
    
    <head>
        <title>ES6标准入门（第二版）</title>
    </head>
    
    <body>
        <script type="text/javascript">
        //1、解构赋值  字符串->字符
        const [a, b, c, d, e] = "abcde";
        alert(a); // a
    
    
    
        //2、数值数组 -> 数值
        var [a, b, c] = [1, 2, 3];
        alert(a); //a
    
    
    
        //3、解构赋值
        var [foo, [
            [bar], baz
        ]] = [1, [
            [2]
        ], 3];
        alert(foo); // 1
    
    
    
        // 4、解构赋值->互换数值
        var x = 10;
        var y = 15;
    
        alert("x" + x + ",y" + y); //x:10,y:15
    
        [x, y] = [y, x];
    
        alert("x" + x + ",y" + y); // x:15,y:10
    
    
    
        //5、map 的赋值遍历
        var map = new Map();
        map.set("first", "hello");
        map.set("second", "world");
    
        for (var [key, value] of map) {
            console.log(key + ' is ' + value);
        }
    
    
        //6、Symbol 类型 ： 一个类似字符串的新数据类型
        var s1 = Symbol("foo");
        var s2 = Symbol("bar");
        console.log(typeof(s1));
    
    
        //7、ArrayBuffer对象 ： 代表存储二进制数据的一段内存，不能直接读写
        var buf = new ArrayBuffer(32);
        var dataView = new DataView(buf);
        var da = dataView.getUint8(0);
        console.log(da);
    
    
    
    
        //8、读取arraybuffer 对象内容
        var buffer = new ArrayBuffer(12);
        var x1 = new Int32Array(buffer);
        x1[0] = 1;
        var x2 = new Int32Array(buffer);
        x2[0] = 2;
        console.log(x1);
    
    
    
        //9、二进制数组的应用
        var xhr = new xmlHttpRequest();
        xhr.open("get", url);
        xhr.responseType = "arrayBuffer";
        xhr.onload = function() {
            let arrayBuffer = xhr.response;
        }
        onreadystatechange = function() {
            if (req.readyState === 4) {
                var arrayResponse = xhr.response;
                var dataView = new DataView(arrayResponse);
                var ints = new Uint32Array(dataView.byteLength / 4);
    
                xhrDiv.style.backgroundColor = "red";
                xhrDiv.innerText = "Array is " + ints.length + "uints long";
    
            }
        }
    
    
    
    
    
    
        //10、set数据结构，类似数组，但是成员的值是唯一的
        var s = new Set();
        [2, 3, 4, 5, 6, 7, 2, 3, 4].map(x => s.add(x));
        for (let i in s) {
            console.log(i);
        }
    
    
    
    
    
    
        //11、 set赋值
        var set = new Set([1, 2, 1, 2, 5, 6, 7]);
        console.log(set.length); // 还不支持
        for (let i in set) {
            console.log(i);
        }
    
    
    
        //12、map,set
        var m = new Map();
        var o = { "p": "Hello World!" };
    
        console.log(o); // {p:"Hello World!"}
    
        m.set(o, "content");
    
        console.log(m.get(o)); //content
    
    
    
        //13、菱形 
        document.write("<h1>8</h1>");
        var n = 5;
    
        for (var i = 0; i < 2 * n - 1; i++) {
            if (i < n) {
                for (var j = 0; j < 2 * n - 1; j++) {
                    if (j == n - i - 1 || j == n + i - 1) {
                        document.write("蓝");
                    } else {
                        document.write("一");
                    }
                }
                document.write("</br>");
    
            } else {
                for (var j = 0; j < 2 * n - 1; j++) {
                    if (j == i - n + 1 || j == 3 * n - i - 3) {
                        document.write("蓝");
                    } else {
                        document.write("一");
                    }
                }
                document.write("</br>");
            }
        }
        </script>
    </body>
    
    </html>

转载于:https://www.cnblogs.com/SunlikeLWL/p/7468356.html