全程用AJAX下载文件，并显示下载进度，之后保存文件。
HTML5文件：
<!DOCTYPE html>
<html>
<head>
<title>XMLHttpRequest Download Progress</title>
</head>
<body>
<progress id="p"></progress>
<input type="button" onclick="downloadAndSave();" value="Download"/>
<script>
function downloadAndSave()
{
var progressBar = document.getElementById('p'), xhr = new XMLHttpRequest();
xhr.open('GET', '2');
xhr.responseType = "arraybuffer";
xhr.onprogress = function(event) {
if(event.lengthComputable) {
progressBar.max = event.total;
progressBar.value = event.loaded;
}
};
xhr.onloadend = function(event) {
progressBar.value = event.loaded;
saveByeToFile('2', xhr.response);
};
xhr.send();
}
function saveByeToFile(name, arrayBuffer) {
var byteArray = new Uint8Array(arrayBuffer);
var a = window.document.createElement('a');
a.href = window.URL.createObjectURL(new Blob([ byteArray ], {
type : 'application/octet-stream'
}));
a.download = name;
// Append anchor to body.
document.body.appendChild(a)
a.click();
// Remove anchor from body
document.body.removeChild(a)
}
</script>
</body>
<html>