javascript - Downloading file from ajax result using blob

Question

I use this code to download excel file from server.

$.ajax({
    headers: CLIENT.authorize(),
    url: '/server/url',
    type: 'POST',
    contentType: "application/json; charset=utf-8",
    data: JSON.stringify(jsonData),
    success: function (data) {
        alert('Data size: ' + data.length);
        var blob = new Blob([data], { type: "application/vnd.ms-excel" });
        alert('BLOB SIZE: ' + data.length);
        var URL = window.URL || window.webkitURL;
        var downloadUrl = URL.createObjectURL(blob);
        document.location = downloadUrl;
    },
});

The problem I experience is that even though data and blob sizes are identical, the moment document.location gets assigned I'm prompted to download almoste two times larger excel file. And when I try to open it, excel complains about wrong file format and opened file contains a lot of garbage, even though required text is still there.

Any ideas what is causing this and how to avoid it?

Answer 1

So I solved the problem using AJAX 2. It natively supports binary streams. You can't use jQuery for that, unless you base64 encode everything, apparently.

Working code looks like this:

var xhr = new XMLHttpRequest();
xhr.open('POST', '/le/url', true);
xhr.responseType = 'blob';
$.each(SERVER.authorization(), function(k, v) {
    xhr.setRequestHeader(k, v);
});
xhr.setRequestHeader('Content-type', 'application/json; charset=utf-8');
xhr.onload = function(e) {
    preloader.modal('hide');
    if (this.status == 200) {
        var blob = new Blob([this.response], {type: 'application/vnd.ms-excel'});
        var downloadUrl = URL.createObjectURL(blob);
        var a = document.createElement("a");
        a.href = downloadUrl;
        a.download = "data.xls";
        document.body.appendChild(a);
        a.click();
    } else {
        alert('Unable to download excel.')
    }
};
xhr.send(JSON.stringify(jsonData));

Hope this helps.