html2canvas.js

// ...
// all of the rest HTML2Canvas.js
(function() {
    html2canvas(document.body, {
        onrendered: function(canvas) {
            var img = document.createElement('img');
            img.src = canvas.toDataURL("image/png");
            img.style.visibility = 'hidden';
            img.id = "fullPageScreenshotId";
            document.body.appendChild(img);
        }
    });
})();