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);  
      
    }  
      
      
    }