There is a JavaScript function, of which I have zero control of the code, which calls a function that I wrote. My function uses DOM
to generate an iFrame, defines it's src and then appends it
to another DOM element. However, before my function returns, and thus allows continued execution of the containing function, it is imperative that the iFrame be fully loaded.
Here are the things that I have tried and why they do not work :
1. The SetTimeout option :
99.999% of the time, this is THE answer. As a matter of fact, in the past decade that I have been mentoring in JavaScript, I have always insisted that code could always be refactored
to use this option, and never believed a scenario existed where that was not the case. Well, I finally found one! The problem is that because my function is being called inline, if the very next line is executed before my iFrame finishes loading, it totally neuters my script, and since the moment my script completes, the external script continues. A callback of sorts will not work
2. The "Do nothing" loop :This option you use while(//iFrame is not loaded){//do nothing}. In theory this would not return until the frame is loaded. The problem is that since this hogs all the resources, the iFrame never loads. This trick, although horribly unprofessional, dirty etc. will work when you just need an inline delay, but since I require an external thread
to complete, it will not.In FF, after a few seconds, it pauses the script and an alert pops up stating that there is an unresponsive script. While that alert is up, the iFrame is able
to load, and then my function is able
to return, but having the browser frozen for 10 seconds, and then requiring the user
to correctly dismiss an error is a no go.
3. The model dialogue :
I was inspired by the fact that the FF popup allowed the iFrame
to load while halting the execution of the function, and thinking about it, I realized that it is because the modal dialogue, is a way of halting execution yet allowing other threads
to continue! Brilliant, so I decided
to try other modal options. Things like alert() work beautifully! When it pops up, even if only up for 1/10th of a second, the iFrame is able
to complete, and all works great. And just in case the 1/10 of a second is not sufficient, I can put the model dialogue in the while loop from solution 2, and it would ensure that the iFrame is loaded in time. Sweet right? Except for the fact that I now have
to pop up a very unprofessional dialogue for the user
to dismiss in order
to run my script. I fought with myself about this cost/benefit of this action, but then I encountered a scenario where my code was called 10 times on a single page! Having
to dismiss 10 alerts before acessing a page?! That reminds me of the late 90s script kiddie pages, and is NOT an option.
4. A gazillion other delay script out there:There are about 10 jQuery delay or sleep functions, some of them actually quite cleverly developed, but none worked. A few prototype options, and again, none I found could do it! A dozen or so other libraries and frameworks claimed they had what I needed, but alas they all conspired
to give me false hope.
I am convinced that since a built in model dialogue can halt execution, while allowing other threads
to continue, there must be some code accessible way
to do the same thing with out user input.
The Code is literally thousands upon thousands of lines and is proprietary, so I wrote this little example of the problem for you
to work with. It is important
to note the ONLY code you are able
to change is in the onlyThingYouCanChange function
Test File :
<html>
<head>
</head>
</html>
<body>
<div id='iFrameHolder'></div>
<script type='text/javascript'>
function unChangeableFunction()
{
new_iFrame = onlyThingYouCanChange(document.getElementById('iFrameHolder'));
new_iFrame_doc = (new_iFrame.contentWindow || new_iFrame.contentDocument);
if(new_iFrame_doc.document)new_iFrame_doc=new_iFrame_doc.document;
new_iFrame_body = new_iFrame_doc.body;
if(new_iFrame_body.innerHTML != 'Loaded?')
{
//The world explodes!!!
alert('you just blew up the world! Way
to go!');
}
else
{
alert('wow, you did it! Way
to go!');
}
}
var iFrameLoaded = false;
function onlyThingYouCanChange(objectToAppendIFrameTo)
{
iFrameLoaded = false;
iframe=document.createElement('iframe');
iframe.onload = new Function('iFrameLoaded = true');
iframe.src = 'blank_frame.html'; //Must use an HTML doc on the server because there is a very specific DOM structure that must be maintained.
objectToAppendIFrameTo.appendChild(iframe);
var it = 0;
while(!iFrameLoaded) //I put the limit on here so you don't
{
//If I was able
to put some sort of delay here that paused the exicution of the script, but did not halt all other browser threads, and did not require user interaction we'd be golden!
//alert('test'); //This would work if it did not require user interaction!
}
return iframe;
}
unChangeableFunction();
</script>
</body>
blank_frame.html :
<html>
<head>
</head>
<body style='margin:0px'>Loaded?</body>
</html>
