injects math into a canvas wiki page

inject_math.js

(function(window){
  // inside of here window is the iframe
  var document = window.document;

  function loadScriptWithCallback(url, callback) {
    var head = document.getElementsByTagName("head")[0] || document.documentElement;
		var script = document.createElement("script");
		script.src = url;
		script.onload = script.onreadystatechange = function() {
			callback.call(window);
		};
		head.insertBefore( script, head.firstChild );
  }

  loadScriptWithCallback("http://ajax.googleapis.com/ajax/libs/jquery/1.4.4/jquery.js", function(){
    this.jQuery(function($){
      // in here $ is our new jquery, window is the iframe, and document is the iframe document
      $("head").append('<link rel="stylesheet" type="text/css" href="http://laughinghan.github.com/mathquill/mathquill.css">');
      $.getScript('http://laughinghan.github.com/mathquill/mathquill.js', function(){
        var equation = "\\frac{d}{dx}\\sqrt{x}=\\frac{d}{dx}x^{\\frac{1}{2}}=\\frac{1}{2}x^{-\\frac{1}{2}}=\\frac{1}{2\\sqrt{x}}";
        $('<span>'+equation+'</span>').appendTo('body').mathquill('editable');
        console.log($el);
      });
    });
  });
})($("#wiki_page_body_ifr")[0].contentWindow);