Javascript / jQuery - How to convert Media and Image data into binary text format

You can find your answer in this post get image data in javascript

function getBase64Image(img) {
    // Create an empty canvas element
    var canvas = document.createElement("canvas");
    canvas.width = img.width;
    canvas.height = img.height;

    // Copy the image contents to the canvas
    var ctx = canvas.getContext("2d");
    ctx.drawImage(img, 0, 0);

    // Get the data-URL formatted image
    // Firefox supports PNG and JPEG. You could check img.src to guess the
    // original format, but be aware the using "image/jpg" will re-encode the image.
    var dataURL = canvas.toDataURL("image/png");

    return dataURL.replace(/^data:image\/(png|jpg);base64,/, "");
}

You need to pass the img tag to this function. For further details see Convert an image into binary data in javascript

A few times already I read that jQuery doesn't provide functionality to download binary data and have it pass on to JavaScript as a string. Then I ran into this question. That got me thinking and I wrote a wrapper around $.ajax() looking like this (yes, it's simplified to show the main bits):

ajaxWrapper = function(url, dataType, callback, headers) {
    return $.ajax({
        url: url,
        dataType: dataType == "binary" ? "text" : dataType,
        mimeType: dataType == "binary" ? "text/plain; charset=x-user-defined" : undefined,
        headers: headers || {}
    }).done(function(data, status, jqXHR) {
        callback(data, status, jqXHR);
    });
}

And then in case you are dealing with Unicode the callback contains this line:

data = btoa(unescape(encodeURIComponent(data)));

or otherwise simply

data = btoa(data);

In other words if you read through the documentation of $.ajax() you simply add a dataType "binary".

Note that I use jQuery 1.7.1, but I don't see why it shouldn't work in later versions, too.