js原生的预加载图片

- 日理万妓 2022-08-11 00:42 275阅读 0赞

没事自己搞了一个预加载图片，这个东西貌似比较简单，

好吧，其实就是嫌别人的大，麻烦

code：

//=======================
    //疯狂紫萧的懒加载
    //为了预加载网页中的图片而设计
    //=======================
    
    //预加载
    //@pagram list:加载列表,progress:每次加载调用方法,complete:完成之后的回调
    //<img class="lazy" data-src="images/4.gif" />
    //<div class="lazy" data-background_image="images/5.jpg"></div>
    //lazy($(".lazy"), function (num) {load.load(num);}, init);
    function lazy(list, progress, complete) {
        var list = list || [];
        var progress = progress || function () { };
        var complete = complete || function () { };
        var res = [];
        var count = list.length;
        var index = 0;
                
        if (list.length == 0)
        {
            complete && complete(res);
        }
    
        for (var i = 0; i < count; i++) {
            res[i] = new Image();
            res[i].index = i;
    
            if (list[i].dataset.src) {
                res[i].onload = function () {
                    index++;
                    list[this.index].removeAttribute("data-src");
                    list[this.index].src = this.src;
                    progress(index / count * 100);
                    index >= count && complete();
                }
                res[i].onerror = function () {
                    index++;
                    index >= count && complete();
                }
                res[i].src = list[i].dataset.src;
            }
            if (list[i].dataset.background_image) {
                res[i].onload = function () {
                    index++;
                    list[this.index].removeAttribute("data-background_image");
                    list[this.index].style.backgroundImage = "url(" + this.src + ")";
                    progress(index / count * 100);
                    index >= count && complete();
                }
                res[i].onerror = function () {
                    index++;
                    index >= count && complete(res);
                }
                res[i].src = list[i].dataset.background_image;
            }
        }
    }