Develop Reference

Running external JS function with document.write asyncronously

We have a website that is supposed to be loading a logo provided by a 3rd party (the logo is a link that allows users to see that our site has been verified by that 3rd party.)
To get this to work, we're told to include a short script in the head
<script type="text/javascript">
//<![CDATA[
var tlJsHost = ((window.location.protocol == "https:") ?
"https://secure.comodo.com/" : "http://www.trustlogo.com/");
document.write(unescape("%3Cscript src='" + tlJsHost +
"trustlogo/javascript/trustlogo.js'
type='text/javascript'%3E%3C/script%3E"));
//]]>
</script>
And another script in the body:
<script language="JavaScript" type="text/javascript">
TrustLogo("https://ourfakesite.com/logo.png", "CL1", "none");
</script>
This all worked fine, initially: the external script is loaded, the function is run, the logo shows up. Perfect.
The problem occurred when the remote site got really slow...all of our pages that load this logo suddenly became very slow as well, since the script is running synchronously.
Ideally, I'd like this to work as if it were designed as an ajax type call...load the page, and after the page is loaded, attempt to load the extra content.
I've tried some combinations of async/defer and using things like ajax, but it seems that because the JS is using a document.write, if the page is fully loaded, the document.write blows away the existing document before writing the new data; the page loads...and then disappears and the logo appears. (I've seen some commentary explaining that this is expected behavior when document.write is used after the page is loaded.)
Is there a way to do this? Is there an alternate path I'm not considering?

Looking at https://secure.comodo.com/trustlogo/javascript/trustlogo.js, the TrustLogo function itself uses document.write (indirectly, the code is minified, but eventually it does), which means you can't use those scripts asynchronously. If you make the first script asynchronous and append that JavaScript file another way, then you have to make the second script asynchronous, and that would mean document.write (within the TrustLogo function) would be called after the main HTML parsing is complete, which in turn means that there'd be an implicit document.open, which would erase your page. :-(
Of course...you could put all of that in an iframe on your main page, so that only the iframe, not your whole page, is impacted. Provided that's not a violation of the terms of use of the logo (obviously, you'd use a relative path for the iframe so their code sees the right domain and such).

JS file is loaded but not being executed

I have a project running on Symfony with angular js and its all working good except for a strange thing.
I added a JavaScript file to execute some JQuery functions i already tested in the browser console and they are all working good with no errors the problem is when I inspect element i can see the file being called in the head and i can also see it in the sources I can even open the link and see the file.
But for some reason the functions in there are not being called executed.
following the images to prove that its loading with no errors.
Edit:
Its not about putting the code in ready function or not

$(document).ready is firing before angular has loaded the content onto the page.
So it might be the possibility of your jQuery plugin calls before your Angular loads the content onto the page.
what you need to do is somehow, call your jQuery plugin once your Angular gets init or you can turns your code into directive.

My script file was also loading but not executing but I had a different issue, basically avoid using href attribute in script tag and instead use src

basic javascript alert not working in Intel XDK code editor

I'm starting fresh with a new blank Intel project and I haven't even started coding yet. I'm just setting up my file tree and making sure the html and javascript pages are connected via the right anchors and script paths. My first .js file won't work though.
I've included a screen shot of test code and the errors. I know the syntax is correct because it works when I put it in <script> tags in the index.html file.
I'm getting "document not defined" and "alert not defined" errors or the js page though. I don't know what that means.
I've considered that my script tag src path in the index file is incorrect, but all the paths are relative in the commented out template script tags intel provides on the index page right out of the box, so why would I have to use an absolute path?
My path is: js/Test.js and it's the last script tag before the body.
Index.html file
*****UPDATE****
So I've tried a few things and it's still not working but I HAVE managed to get my errors down to just one inexplicable "missing semicolon", which will turn into an "unnecessary semicolon" error if I place it.
Any way as per the first screen shot you'll see that I wasn't placing the document object inside of an explicitly declared variable. Once I did that and accessed it through dot syntax instead of an equal sign then I stopped getting the error. I included this screenshot to show my work before I made the changes.
so the problem I went on to have is that unless every function or dom object was declared with "Var", I'd get an error. This includes the alert() function which I don't think I've ever seen needing to be declared that way, but I gave the code editor what it wanted and this last screenshot is the results. It's not working, BUT I'm not getting the errors I was before, except for the missing/unnecessary semicolon paradox. Removing it or including it throws an error.

JavaScript can be loaded before or after the HTML, however the way it is done is slightly different depending on how you do it.
For example if you wish to include your JavaScript files within the head of the HTML file then you must wrap your JavaScript code with either DOMContentLoaded or jQuery's $(document).ready().
The common misconception of using window.onload will not fix the issue where the elements have not loaded in correctly.
The Mozilla Developer Network states on this page:
The DOMContentLoaded event is fired when the initial HTML document has been completely loaded and parsed, without waiting for stylesheets, images, and subframes to finish loading. A very different event - load - should be used only to detect a fully-loaded page. It is an incredibly popular mistake to use load where DOMContentLoaded would be much more appropriate, so be cautious.
That quote in itself should prove that onload should not be relied on if you want the full DOM to be loaded properly before you start manipulating it. Instead you should do the following:
Vanilla
document.addEventListener("DOMContentLoaded", function (e) {
/** DOM has been fully loaded here, so manipulation can begin. **/
/** Your code here. **/
});
jQuery
$(document).ready(function () {
/** DOM has been fully loaded here, so manipulation can begin. **/
/** Your code here. **/
});
Click this link to see the difference between vanilla and jQuery.
The second way you can load JavaScript is by having all the script tags within the body but after all the HTML, that way it is guaranteed to load after the HTML.
Example
Try this working example I quickly coded up.
HTML
Replace the content within the body tag of your HTML to the following:
<button id="myJsTest">Click Me!</button>
<div id="clickCounter">Click Count: 0</div>
Replace the contents of your JavaScript with the following:
JavaScript
document.addEventListener("DOMContentLoaded", function() {
var clickCount = 0;
document.getElementById("myJsTest").addEventListener("click", function() {
clickCount++;
document.getElementById("clickCounter").innerText = "Click Count: " + clickCount;
});
});
Then use the Emulate tab in Intel XDK to test it.
Additional Information
When I use Intel XDK and I have an error, I quickly load the file in to the browser and check the console. It can be a really helpful and effective way of squashing those pesky little bugs.
Try using window.alert as alert is defined in the window object.

The reason you're seeing all those "error" messages in the editor window is because you've got the various JSLint/Hint tools loaded in the editor. They're trying to keep you honest and save you lots of time in the debugger chasing potential syntax errors.
The editor inside the XDK is Brackets, it is using standard Brackets extensions to provide those JSLint/Hint tools. You can download it and run it standalone on your system and edit directly within it, you don't have to use the editor inside the XDK (or you can use any other editor you like).
Because the Lint/Hint tools only look at one file at a time, and because your app is normally spread over multiple files, they don't know much about about what's defined in your other files. Likewise, those hint/lint tools need to be told that you're using some of the standard global methods and properties that are expected to be found in a browser (but which may not be found in other JavaScript environments, because JavaScript is no longer limited to just a browser environment -- in fact, your XDK app, aka Cordova app, runs inside a "webview" not in a browser, but that's another story...)
So, you should follow some standard practice of setting up your JSHint/Lint directives at the top of your JS files. For example, this is a good starting point:
/*jslint browser:true, devel:true, white:true, vars:true */
/*global $:false, intel:false */
See the JSHint documentation for details... and see the "Blank Cordova Starter App" in the "Start a New Project" section of the Projects tab for a better blank template to start (there is no real difference between a blank template and a demo app, they are structured identically).
For a more complete and even more instructive app, see the "Hello, Cordova" sample app. Both of those apps can also be found on the Intel XDK GitHub repo.

You are adding the js file that is <script src="js/Test.js"></script> inside header tag.
So js will be first loaded and and it will attach all events to it. But when js is loaded button id="jsTest" is not present because DOM is not loaded.
Solutions :-You can follow either of the approach
Add your js files after DOM is ready
<body>
<button id ="js/Test.js">Test JS</button>
// other HTML tags
<script src = "js/Test.js></script>
</body>
Use window.onload
The load event fires at the end of the document loading process.
window.onload = testJsFile(){
//Your code goes here
}
I will prefer to use the first approach since that also address other issues like page loading time

Try to put the line outside your JS function
document.getElementById(......
inside your html page between
<script>HERE</script>
If this is still no working. Try to add onClick attribute to the button like this:
<button id="" onClick="testJsFile()">
Its also good to use google chrome element inspection while devlopping cuse it will give you error msg for all these things.

Javascript onload after redirect

in my Javascript code I am loading a page, and then would like to perform some functions. I tried to use solutions like window.onload, but that is after my html (blank page with just the JS) loads, I need the function to perform after the page I am reffering to is loaded.
I am using this code:
this.document.location.href = myurl;
And after this loads, I would like to call some function. Is there a way to do so?
Thanks
EDIT:
I can not edit the target page source code.

When you change the value of document.location.href, you are essentially doing a redirect.
You can either just do whatever you want to do within the loaded page itself or if you don't have cross domain issues, do xhr of the page you're wanting to load dynamically, query the body, replace content of your current body and also replace head contents i.e. style, title and scripts etc. You could then execute any script you want.
Extra note: This is quite a tricky thing to do, I've done this a few times before - and its proven quite problematic due to the fact that you don't actually get a fully parsed document object that you can just query so simply, you only receive a huge string. One hack that I've thought of using is actually just loading everything within an iframe allowing easy querying which is actually documented - extra reading here

window.load takes forever to fire because it waits for all images and assets to load on the page.
It sounds like the best solution for you would be to poll for the document to be finished loading. Here's a simple example:
(function poll(){
if(document.readyState === "complete"
{
// Your code here
}
else
setTimeout(poll,500);
})();

Place the 'window.onload = myFunction(){...}' inside the page, which will be loaded.
this.document.location.href
will open the page like you typed it into the browser address bar and your onload-script in the old page will not be executed in the new one.
By the way, you can shortcut it to document.location = myUrl
See the Document-API at Mozilla

loading a js file asynchronously from a js file that loads asynchronously

I had a javascript file(initial.js) on the page inserted through the script tag like so:
<script src="initial.js"></script>
This file creates dom elements(let say two links) and also loads another jQuery plugin(plugin.js) asynchronously via jQuery ajax method. Clicking on those two links brings up a module from the jQuery plugin(plugin.js).
The javascript file(initial.js) was then modified to load asynchronously on the page via jQuery ajax instead of via script tag. This has resulted in some events not getting attached to the links intermittently and this results in the plugin not being called.
I believe the browser is loading the async scripts in its own order and hence the links fail to launch the plugin intermittently. Any pointers to resolve this issue with this new set up?

At a high-level, I think you need to look into something like require.js. Alternatively, you could look into some jQuery event handling code which allows you to listen on load events of calls which may help you determine when one script loaded before loading the next one.

You have probably tried something like this in the past:
var output;
$.get('data.php',function(data){
output=data;
});
alert(output);
You will get an undefined error because Javascript doesn't wait around for the AJAX call to be returned before moving onto the next code.
Same thing goes for scripts. If you place multiple calls to multiple scripts, you will probably get the smallest one returned the quickest, and that script executed. If you load a script that is 10kb and then one that is 1kb, the 1kb script will probably return the quickest and then be executed even though it was called after the 10kb script.
To correct this, you could make a queue system and then only load each script after the previous has loaded:
var scripts=['script1.js','script2.js','script3.js'];
$(document).ready(function(){
loadScript();
});
function loadScript(){
if(sendQueue.length==0)
return;
$.getScript(scripts[0],function(){
scripts=scripts.slice(1);
loadScript();
});
}
But if you are loading scripts from within scripts from within scripts... very Inception like, then this still may not work.