要掌握上傳進度有一個關鍵: Client Script必須掌握檔案大小以及已上傳資料量，才可能計算上傳百分比回報狀態。傳統使用<input type="file">選取檔案配合<input type="submit">送出鈕的做法，一來無法得知所選取檔案大小，二來在按下POST鈕後Script即失去主導權，一切交由瀏覽器主控， 更別奢談得知上傳進度。在從桌面拖拉檔案到網頁一 文提到的HTML5 File API，一舉突破JavaScript無從得知檔案大小的盲點，邁進一大步。而透過XHR(XMLHttpRequest)，改用 jQuery.ajax()非同步上傳檔案，便能在上傳過程繼續更新網頁回報進度。這樣子只剩下一個挑戰 -- 如何得知已上傳資料量?
好消息! 隨著瀏覽器日新月異，XHR也跟著進化，HTML5世代瀏覽器(IE需為IE10+，IE9又哭哭了...)已內建XMLHttpRequest Level 2(XHR2)，增加不少新功能，包含直接處理ArrayBuffer/Blob等二進位資料的能力，也多了onprogress事件，能在傳輸過程中持續觸發回報上傳進度! 有了新武器，要實現上傳進度回報就簡單多了。
原始介紹文章出自於此
@{
Layout = null;
}
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width" />
<title>Ajax Upload Lab</title>
<style>
.item {
background-color: #6699CC; border: 1px solid gray;
font-family: 'Courier New'; font-size: 8.5pt;
margin-bottom: 6px; padding: 3px; color: yellow;
box-shadow: 3px 3px 3px 1px rgba(128, 128, 128, 0.7);
}
.item .name { text-shadow: 1px 1px gray; }
.prg-zone { margin-top: 10px; }
.bar {
background-color: #666666;
height: 15px; position: relative;
margin: 3px; margin-top: 6px;
margin-bottom: 6px; border: 1px solid #ccc;
border-top-color: #444; border-left-color: #444;
}
.bar > div {
position: absolute; color: white; font-size: 8pt;
}
.bar .color-bar {
background-color: #99bb33; top: 0px; bottom: 0px;
left: 0px;
}
.bar .status { top: 0px; left: 6px; }
.bar .progress { top: 0px; right: 4px; }
</style>
</head>
<body>
<div>
<input type="file" id="fileSelector" multiple
data-bind="event: { change: selectorChange }" />
<input type="button" value="Upload" data-bind="click: upload" />
</div>
<div data-bind="foreach: files" class="prg-zone">
<div class="item">
<div data-bind="text: name" class="name"></div>
<div class="bar">
<div class="color-bar" data-bind="attr: { 'style': widthStyle }"></div>
<div class="status" data-bind="text: status"></div>
<div class="progress" data-bind="text: progress"></div>
</div>
</div>
</div>
<script src="~/Scripts/jquery-2.1.0.js"></script>
<script src="~/Scripts/knockout-3.1.0.debug.js"></script>
<script>
$(function () {
function viewModel() {
var self = this;
self.files = ko.observableArray();
self.selectorChange = function (item, e) {
self.files.removeAll();
$.each(e.target.files, function (i, file) {
//加入額外屬性
file.uploadedBytes = ko.observable(0); //已上傳Bytes
file.percentage = ko.computed(function () { //上傳百分比
return (file.uploadedBytes() * 100 / file.size).toFixed(1);
});
file.widthStyle = ko.computed(function () {
return "right:" + (100 - file.percentage()) + "%";
});
//上傳進度數字顯示
file.progress = ko.computed(function () {
var perc = file.percentage();
return file.uploadedBytes.peek() + "/" + file.size +
"(" + perc + "%)";
});
file.message = ko.observable();
file.status = ko.computed(function () {
var msg = file.message(), perc = file.percentage();
if (msg) return msg;
if (perc == 0) return "Waiting";
else if (perc == 100) return "Done";
else return "Uploading...";
});
self.files.push(file);
});
};
self.upload = function () {
$.each(self.files(), function (i, file) {
var reader = new FileReader();
reader.onload = function (e) {
var data = e.target.result;
//https://gist.github.com/HenrikJoreteg/2502497
//以XHR上傳原始格式
$.ajax({
type: "POST",
url: "@Url.Content("~/xhr2/upload")" + "?file=" + file.name,
contentType: "application/octect-stream",
processData: false, //不做任何處理，只上傳原始資料
data: data,
xhr: function () {
//建立XHR時，加掛onprogress事件
var xhr = $.ajaxSettings.xhr();
xhr.upload.onprogress = function (evt) {
file.uploadedBytes(evt.loaded);
};
return xhr;
}
});
};
reader.readAsArrayBuffer(file);
});
};
}
var vm = new viewModel();
ko.applyBindings(vm);
});
</script>
</body>
</html>
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