HTML5托拽上传(XMLHttpRequest和Google Gears)

      HTML5的拖拽上传功能可拆分为两个部分实现，一个是对象的拖拽功能，另一个是上传功能。拖拽功能的实现基于HTML5 DOM对象的拖拽事件 ，FF3.6+和Chrome7+都实现了该功能，所以不用做特别的兼容，代码如下：

 

    var uploadZone=$("uploadZone"),
        iptFile,
        file,
        ffUpload=new FirefoxFileUpload("http://localhost/upload/a.php"); 
        //chromeUpload=new ChromeFileUpload("http://localhost/upload/a.php");
        
    function focus(state){
        uploadZone.style.backgroundColor=state?"#f0ab0c":"";
    }



    uploadZone.addEventListener("dragenter",function(e){
        focus(true);
        e.stopPropagation();
        e.preventDefault();
    },false);

    uploadZone.addEventListener("dragleave",function(e){
        focus(false);

    },false);

    uploadZone.addEventListener("dragover",function(e){
        e.stopPropagation();
        e.preventDefault();
    },false);

    uploadZone.addEventListener("drop",function(e){
        e.stopPropagation();
        e.preventDefault();
        focus(false);
        
        //Firefox上传
        ffUpload.xhr.upload.onprogress=function(e){
            var w=$("pgBorder").offsetWidth;
            
            $("progress").style.width=e.loaded/e.total*w+"px";
        };
        ffUpload.xhr.upload.onload=function(){
            $("progress").style.width=$("pgBorder").offsetWidth+"px";
        };
        ffUpload.upload(ffUpload.getFile(e));

        
        //Chrome上传
    //    chromeUpload.xhr.upload.onprogress=function(e){
    //        console.log(e.loaded/e.total*100+"%");
    //    };
    //    chromeUpload.upload(chromeUpload.getFile(e));
        
    },false);

而HTML5的文件传输功能则是基于两套实现方式：
    firefox：
        fileReader.readAsBinaryString 读取二进制串
        XMLHttpRequest.sendAsBinary 以二进制的格式发送给服务器端（真给力）
    
    chrome：
        gears API

因为XMLHttpRequest.sendAsBinary目前还没有被w3c列为标准，所以只能在Firefox中私有地使用。

以下是简单封装的两个浏览器的上传类
      

 var FirefoxFileUpload=function(url,dataName){
                this.xhr=new XMLHttpRequest();
                
                this.__file=null;
                this.__fileReader=new FileReader();
                this.__url=url;
                this.__dataName=dataName || "FileData";
                
                this.__initReader();
            };
            FirefoxFileUpload.prototype={
                upload:function(file){
                    if(!file){
                        return;
                    }
                    
                    this.__file=file;
                    this.__fileReader.readAsBinaryString(this.__file);
                },
                
                getFile:function(e){
                    return e.dataTransfer.files[0];
                },
                
                __send:function(){
                    var xhr=this.xhr,
                        boundary="----------BOUNDARY"+(new Date()).getTime(),
                        body=this.__getBody(this.__fileReader.result,boundary);
                    
                    xhr.open("post",this.__url,true);
                    xhr.setRequestHeader("Content-Type","multipart/form-data, boundary="+boundary);
                    xhr.setRequestHeader("Content-Length",this.__file.size);

                    xhr.sendAsBinary(body);
                },
                
                __initReader:function(){
                    var me=this;
                    this.__fileReader.addEventListener("load",function(){
                        me.__send();
                    },false);
                },
                
                __getBody:function(readerResult,boundary){
                    return ['--',boundary,'\r\n',
                            'content-disposition: form-data; name="',this.__dataName,'"; filename="',encodeURI(this.__file.name),'"\r\n',
                            'Content-Type: ',this.__file.type,'\r\n\r\n',
                             readerResult,"\r\n",
                            '--',boundary,'--\r\n'
                        ].join("");
                }
                
            };