jQuery或者js保存文件到本地

使用jQuery或者js，点击保存button，弹出保存文件的对话框，将服务器上的文件以xml格式保存到本地，怎么做？

function fake_click(obj) {    var ev = document.createEvent("MouseEvents");    ev.initMouseEvent(        "click", true, false, window, 0, 0, 0, 0, 0        , false, false, false, false, 0, null        );    obj.dispatchEvent(ev);}function export_raw(name, data) {    var urlObject = window.URL || window.webkitURL || window;    var export_blob = new Blob([data]);    var save_link = document.createElementNS("http://www.w3.org/1999/xhtml", "a")    save_link.href = urlObject.createObjectURL(export_blob);    save_link.download = name;    fake_click(save_link);}$('a').click(function() {export_raw('test.html', 'hello world');});

<a href="#">保存文件</a>