Thursday, December 23, 2010

Few more thoughts on script loaders in websites

Last week JS GURU Steve Souders (Google) released his ControlJS project. The goal of the project is that to provide freedom to developer to load js files and execute them later on a page as per user action.
In our, we already applied same technique. we load heavy dynamic pages in overlay (modal box) through AJAX but initially we encountered with one problem .. if we load a page with AJAX and suppose that page contain inline JS code .. then that JS code will not be executed. so finally we used some technique/ hack and solved issue.

Actually we parse whole inline JS and CSS that comes in script and css html tag and evaled it later once we get ajax success callback. here is code for same.

function ajax_parseJs(obj)
    var scriptTags = obj.getElementsByTagName('SCRIPT');
    var string = '';
    var jsCode = '';
    for(var no=0;no<scriptTags.length;no++){
            var head = document.getElementsByTagName("head")[0];
            var scriptObj = document.createElement("script");

            scriptObj.setAttribute("type", "text/javascript");
            scriptObj.setAttribute("src", scriptTags[no].src);
                jsCode = jsCode + scriptTags[no].text + 'n';
                jsCode = jsCode + scriptTags[no].innerHTML;


function evaluateCss(obj)
   var cssTags = obj.getElementsByTagName('STYLE');
   var head = document.getElementsByTagName('HEAD')[0];
   for(var no=0;no<cssTags.length;no++){
function ajax_installScript(script)
    if (!script)
    if (window.execScript){
    }else if(window.jQuery && jQuery.browser.safari){ // safari detection in jQuery
        window.setTimeout( script, 0 );

So i thought that can we do same for script loading ? i think it's not a big deal to load script and execute it
when developer want. here is code for same.

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;
    } else {  //Others
        script.onload = function(){
    script.src = url;

var script = document.createElement("script");
script.type = "text/cache";
script.src = "foo.js";
script.onload = function(){
    //script has been loaded but not executed
document.body.insertBefore(script, document.body.firstChild);

//at some point later

Hope above techniques are clear and you don't have any doubts .. if still you have any query then write me on mail @ tussion @ ymail dot com

Happy coding ... Enjoy XMAS holidays ...

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