ajax实现文件上传进度条

$.ajax({
type: 'POST',
url: "/",
data: {},
beforeSend: function(XMLHttpRequest)
{
//Upload progress
XMLHttpRequest.upload.addEventListener("progress", function(evt){
if (evt.lengthComputable) {
var percentComplete = evt.loaded / evt.total;
//Do something with upload progress
}
}, false);
//Download progress
XMLHttpRequest.addEventListener("progress", function(evt){
if (evt.lengthComputable) {
var percentComplete = evt.loaded / evt.total;
//Do something with download progress
}
}, false);
},
success: function(data){
//Do something success-ish
}
});