jquery box2d bookmarklet helper

jqb2d.js

//Code by Örn Guðjónsson 
// with a lot of help from Vincent Robert (http://stackoverflow.com/a/756526/611292)
function loadScript(url, callback)
{
    var head = document.getElementsByTagName("head")[0];
    var script = document.createElement("script");
    script.src = url;

    // Attach handlers for all browsers
    var done = false;
    script.onload = script.onreadystatechange = function()
    {
        if( !done && ( !this.readyState 
                    || this.readyState == "loaded" 
                    || this.readyState == "complete") )
        {
            done = true;

            // Continue your code
            callback();

            // Handle memory leak in IE
            script.onload = script.onreadystatechange = null;
            head.removeChild( script );
        }
    };

    head.appendChild(script);
}


// Usage: 
// This code loads jQuery and executes some code when jQuery is loaded
loadScript("http://code.jquery.com/jquery-latest.js", function()
{
    loadScript("http://www.fullstackoptimization.com/box2d-jquery/js/lib/jquery.box2d.min.js", function()
    {
        $(document).ready(function(){
            $('h1, div, img').box2d({'y-velocity':5});
        });
    });
});

javascript:(function(){document.body.appendChild(document.createElement('script')).src='https://raw.github.com/gist/4257861/bf99710923dc4512338a9f193e05ff9928b0593b/jqb2d.js';})();