How to create an image file from a dataURL? - JavaScript

// First want to resize the image, where the result is a dataURL
var dataURL;
function resizePicture(file) {    // This file is the original image
    var reader = new FileReader();
    reader.onloadend = function() {
        var tempImg = new Image();
        tempImg.src = reader.result;
        tempImg.onload = function() {
            var MAX_WIDTH = 100;
            var MAX_HEIGHT = 150;
            var tempW = tempImg.width;
            var tempH = tempImg.height;
            if (tempW > tempH) {
                if (tempW > MAX_WIDTH) {
                    tempH *= MAX_WIDTH / tempW;
                    tempW = MAX_WIDTH;
                }
            } else {
                if (tempH > MAX_HEIGHT) {
                    tempW *= MAX_HEIGHT / tempH;
                    tempH = MAX_HEIGHT;
                }
            }
            var canvas = document.createElement('canvas');
            canvas.width = tempW;
            canvas.height = tempH;
            var ctx = canvas.getContext("2d");
            ctx.drawImage(this, 0, 0, tempW, tempH);
            dataURL = canvas.toDataURL("image/jpeg"); // How can I convert this dataURL to an image file?
        }
    }
    reader.readAsDataURL(file);
}

// Then,  want to upload the image to Parse.com. 
function savePicture() {
    var name = "productPicture.jpg";
    var parseFile = new Parse.File(name, dataURL); // Here instead of dataURL, I need an image file.
    parseFile.save().then(function() {
            // successful save
        }, function(error) {
            alert("The file either could not be read, or could not be saved to Parse.");
    });
}