dom doesn't exist until after window.onload

Demonstrate that attempting to access the DOM with javascript loaded in the html head will not work unless you wrap it in something like window.onload

by nikdtu

HTML

<body>

</body>

JavaScript

window.onload = function() {
   alert('Page Loaded. Loading script now ....');
   var url = 'https://secure.echosign.com/public/widget?f=8KX2X55PXF274A';
   loadScript(url, callback)
}

var callback = function() {
	alert('Script Loaded !');
}

function loadScript(url, callback){

    var script = document.createElement("script")
    script.type = "text/javascript";

    if (script.readyState){  //IE
        script.onreadystatechange = function(){
            if (script.readyState == "loaded" ||
                    script.readyState == "complete"){
                script.onreadystatechange = null;
                callback();
            }
        };
    } else {  //Others
        script.onload = function(){
            callback();
        };
    }

    script.src = url;
    document.getElementsByTagName("head")[0].appendChild(script);
}