将HTML5中的文件拖拽封装成了类

    drag.js:                document.write("<script language='javascript' src='utility.js'></script>");                ////        //要放在哪个容器，容器的ID        ////        function FileDrager(cntId){        this.containerId = cntId;        }                FileDrager.prototype = {                // 判断是否图片        isImage : function(type) {                    switch (type) {                    case 'image/jpeg':                    case 'image/png':                    case 'image/gif':                    case 'image/bmp':                    case 'image/jpg':                        return true;                    default:                        return false;                    }        },                ////初始化        Init : function(){            ////获得放图片的容器            var ctn = $(this.containerId);                ctn.addEventListener('dragover',  function(evt) {                    evt.stopPropagation();                    evt.preventDefault();                }, false);                        ctn.addEventListener('drop', function(e) {                e.stopPropagation();        e.preventDefault();                var fileList  = e.dataTransfer.files,　　//获取拖拽文件        oImg = document.createElement('img'),        reader = new FileReader();                var c = ctn;        var x = e.clientX;        var y = e.clientY;                        reader.onload = function(evt) {        oImg.src = this.result;                oImg.style.position = "absolute";        oImg.style.left = x;        oImg.style.top = y;                c.appendChild(oImg);        }        reader.readAsDataURL(fileList[0]);                }, false);                }                        }