how to load javascript dynamically

Question

I try to load some js files dynamically,for example:

function openInforWindow(){
 //check if the InforWinow.js has been loaded or not
 if(window.InforWindow){
 //do the right thing
 }
 else {
 loadJs('xxxxxx/InforWindow.js');
 // do the right thing
 //but here ,the infowindow is not definded yet.
 }
}
function loadJs(filename){
 var fileref=document.createElement('script')
 fileref.setAttribute("type","text/javascript")
 fileref.setAttribute("src", filename)
 if (typeof fileref!="undefined")
 document.getElementsByTagName("head")[0].appendChild(fileref)
}

How to make sure that the vars or functions in the js which is dynamically loaded can be add to the javascript execute environment so I can use them ?

• Birey: where are you using the parameter "filename"? "js" should be filename i guess. in the line fileref.setAttribute("src",filename)
• Birey: You still got it wrong,ie it is still inside double quotes which makes it a string not a variable.

Answer 1

adding a script element isn't a blocking operation, this means that your loadJs method returns immediately when your external script isn't even loaded (nor interpreted). You have to wait for it to load.

function openInforWindow(){
 //check if the InforWinow.js has been loaded or not
 if(window.InforWindow){
 //do the right thing
 }
 else {
 var loadHandler = function() {
 //do stuff with inforWindow 
 };
 loadJs('xxxxxx/InforWindow.js', loadHandler);
 }
}
function loadJs(filename, handler){
 var fileref=document.createElement('script');
 fileref.setAttribute("type","text/javascript");
 fileref.setAttribute("src", "js");
 fileref.onreadystatechange = function () {
 if (this.readyState == 'complete')handler();
 };
 fileref.onload = handler;
 if (typeof fileref!="undefined")
 document.getElementsByTagName("head")[0].appendChild(fileref);
}

Answer 2

One approach could be to load the script using jQuery's AJAX loader. Example below:

function loadJs(filename, functionToCall){
 $.getScript(filename, functionToCall);
}

Now, you just need to call loadJs("script.js", callback);, and it will first completely load script.js, and then run callback().

• Isaac Lewis: Of course, you don't really need the loadJs wrapper in this example. Equivalent functionality would be achieved by only using the $.getScript() function.

Answer 3

You can dynamically insert a <script/> tag into your document, here is a script that will work in firefox/chrome, you may need a bit of tweaking in IE:

loadJs = function(src) {
 var script = document.createElement('SCRIPT');
 script.setAttribute('src', src);
 document.getElementsByTagName('HEAD')[0].appendChild(script);
}

Then wait for the document.onload event to fire, your window.InforWindow should be loaded at that stage.

document.addEventListener('load', function () {
 // Your logic that uses window.InforWindow goes here
}, false);

Note that IE does the load event listener slightly differently:

document.attachEvent('onload', function() {
 // Your logic that uses window.InforWindow goes here
});