JavaScript File分段上传

var fileSplitSize = 1024 * 1024;
var start=0,end=0;
var i=0;
// 文件段上传
function chunk_upload(button){
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("POST", "/chunk_upload/upload/", false);
xmlhttp.setRequestHeader("X-CSRFToken", button.form['csrfmiddlewaretoken'].value);
var f = button.form;
var file = f['file']['files'][0];
var size=file.size;
end=start+fileSplitSize;
if(end>size){
i=-1;
end=size;
}else{
i+=1;
end=end;
}
　　//按大小切割文件段
var blob = file.slice(start, end);
xmlhttp.setRequestHeader('charset','utf-8');
xmlhttp.setRequestHeader("fileMD5", fileMD5);
xmlhttp.setRequestHeader("start", start);
xmlhttp.setRequestHeader("end", end);
xmlhttp.send(blob);
if(xmlhttp.status==200){
 if(end==size){
 var backtext=xmlhttp.responseText;
 alert(backtext);
 }else{
 alert("上传完成第"+i+"段")
 start=end;
 chunk_upload(button);
 }
 }else{
 alert("上传错误");
 chunk_upload(button);
 }
} 

;(function(window,document){
var myUpload = function(option) {
var file,
fd = new FormData(),
xhr = new XMLHttpRequest(),
loaded, tot, per, uploadUrl,input;
input = document.createElement("input");
input.setAttribute('id',"myUpload-input");
input.setAttribute('type',"file");
input.setAttribute('name',"files");
input.click();
uploadUrl = option.uploadUrl;
callback = option.callback;
uploading = option.uploading;
beforeSend = option.beforeSend;
input.onchange= function(){
file = input.files[0];
if(beforeSend instanceof Function){
if(beforeSend(file) === false){
return false;
}
}
fd.append("files", file);
xhr.onreadystatechange = function() {
if (xhr.readyState == 4 && xhr.status == 200) {
if(callback instanceof Function){
callback(xhr.responseText);
}
}
}
//侦查当前附件上传情况
xhr.upload.onprogress = function(evt) {
loaded = evt.loaded;
tot = evt.total;
per = Math.floor(100 * loaded / tot); //已经上传的百分比
if(uploading instanceof Function){
uploading(per);
}
};
xhr.open("post", uploadUrl);
xhr.send(fd);
}
};
window.myUpload = myUpload;
})(window,document);
//用法
//触发文件上传事件
myUpload({
//上传文件接收地址
uploadUrl: "/async/myUpload.php",
//选择文件后，发送文件前自定义事件
//file为上传的文件信息，可在此处做文件检测、初始化进度条等动作
beforeSend: function(file) {
},
//文件上传完成后回调函数
//res为文件上传信息
callback: function(res) {
},
//返回上传过程中包括上传进度的相关信息
//详细请看res,可在此加入进度条相关代码
uploading: function(res) {
}
});