How to set a header for a HTTP GET request, and trigger file download?

I'm adding another option. The answers above were very useful for me, but I wanted to use jQuery instead of ic-ajax (it seems to have a dependency with Ember when I tried to install through bower). Keep in mind that this solution only works on modern browsers.

In order to implement this on jQuery I used jQuery BinaryTransport. This is a nice plugin to read AJAX responses in binary format.

Then you can do this to download the file and send the headers:

$.ajax({
    url: url,
    type: 'GET',
    dataType: 'binary',
    headers: headers,
    processData: false,
    success: function(blob) {
        var windowUrl = window.URL || window.webkitURL;
        var url = windowUrl.createObjectURL(blob);
        anchor.prop('href', url);
        anchor.prop('download', fileName);
        anchor.get(0).click();
        windowUrl.revokeObjectURL(url);
    }
});

The vars in the above script mean:

• url: the URL of the file
• headers: a Javascript object with the headers to send
• fileName: the filename the user will see when downloading the file
• anchor: it is a DOM element that is needed to simulate the download that must be wrapped with jQuery in this case. For example $('a.download-link').

Try

html

<!-- placeholder , 
    `click` download , `.remove()` options ,
     at js callback , following js 
-->
<a>download</a>

js

        $(document).ready(function () {
            $.ajax({
                // `url` 
                url: '/echo/json/',
                type: "POST",
                dataType: 'json',
                // `file`, data-uri, base64
                data: {
                    json: JSON.stringify({
                        "file": "data:text/plain;base64,YWJj"
                    })
                },
                // `custom header`
                headers: {
                    "x-custom-header": 123
                },
                beforeSend: function (jqxhr) {
                    console.log(this.headers);
                    alert("custom headers" + JSON.stringify(this.headers));
                },
                success: function (data) {
                    // `file download`
                    $("a")
                        .attr({
                        "href": data.file,
                        "download": "file.txt"
                    })
                        .html($("a").attr("download"))
                        .get(0).click();
                    console.log(JSON.parse(JSON.stringify(data)));
                },
                error: function (jqxhr, textStatus, errorThrown) {
                  console.log(textStatus, errorThrown)
                }
            });
        });

jsfiddle http://jsfiddle.net/guest271314/SJYy3/

There are two ways to download a file where the HTTP request requires that a header be set.

The credit for the first goes to @guest271314, and credit for the second goes to @dandavis.

The first method is to use the HTML5 File API to create a temporary local file, and the second is to use base64 encoding in conjunction with a data URI.

The solution I used in my project uses the base64 encoding approach for small files, or when the File API is not available, otherwise using the the File API approach.

Solution:

        var id = 123;

        var req = ic.ajax.raw({
            type: 'GET',
            url: '/api/dowloads/'+id,
            beforeSend: function (request) {
                request.setRequestHeader('token', 'token for '+id);
            },
            processData: false
        });

        var maxSizeForBase64 = 1048576; //1024 * 1024

        req.then(
            function resolve(result) {
                var str = result.response;

                var anchor = $('.vcard-hyperlink');
                var windowUrl = window.URL || window.webkitURL;
                if (str.length > maxSizeForBase64 && typeof windowUrl.createObjectURL === 'function') {
                    var blob = new Blob([result.response], { type: 'text/bin' });
                    var url = windowUrl.createObjectURL(blob);
                    anchor.prop('href', url);
                    anchor.prop('download', id+'.bin');
                    anchor.get(0).click();
                    windowUrl.revokeObjectURL(url);
                }
                else {
                    //use base64 encoding when less than set limit or file API is not available
                    anchor.attr({
                        href: 'data:text/plain;base64,'+FormatUtils.utf8toBase64(result.response),
                        download: id+'.bin',
                    });
                    anchor.get(0).click();
                }

            }.bind(this),
            function reject(err) {
                console.log(err);
            }
        );

Note that I'm not using a raw XMLHttpRequest, and instead using ic-ajax, and should be quite similar to a jQuery.ajax solution.

Note also that you should substitute text/bin and .bin with whatever corresponds to the file type being downloaded.

The implementation of FormatUtils.utf8toBase64 can be found here