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I need to load a third party script file(which I do not have any control), but I want to avoid hanging the page in case the script has an infinite loop in it. I tried calling the javascript file and put it in an updatepanel only on a click of a button but the page still hangs. I even tried putting it in an iframe just to separate it from other controls and the same scenario happens.

Is there really NO way to stop an infinite loop once it has started executing?

jbdeguzman
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    ..not unless a debugger has its grips in there. Why not fire up a debugger and step through it to figure out why it is going into an infinite loop? While you're there you can patch it and submit the fix :) – Simon Whitehead Jul 23 '13 at 10:07
  • @SimonWhitehead, currently the third party js file is fixed and doesn't have an infinite loop anymore but I want to be able to handle the issu anyway. Because it already happened once and I want to avoid having the same problem again. Is there a way to do so? – jbdeguzman Jul 23 '13 at 10:16
  • @Sayse i think there still is. i could not let my page to crash in the future just because of a third party js file that i'm using. My page has to be independent IF that's possible. – jbdeguzman Jul 23 '13 at 10:21

3 Answers3

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You are trying to add handling to a bug that is already fixed, so all that is going to happen is your code is going to become more complex unnecessarily.

I would have faith in the fix that they have produced, and you could look into adding Unit Tests that will allow you to test the bug in a secure manner

Edit If you think the bug still exists then you could create a small test example (i.e your unit test) to send to the third party in hope of a better fix

Sayse
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  • Yes the third party js file works fine now. And to test if I can handle infinite loops inside a js file, I replaced the third party js file with my own js file which has an infinite loop (i.e. while(true);) – jbdeguzman Jul 23 '13 at 10:30
  • I'm sorry I don't understand what you are trying to do, what I was suggesting is you could add a test that uses the third party file to make sure it doesn't crash – Sayse Jul 23 '13 at 10:33
  • i need something to test it on every page load. not test the code now. because like i've said, i do not have any control on the js file. they could change it any minute. so having a unit test now will not be enough. – jbdeguzman Jul 23 '13 at 10:40
  • With the right unit test it could be enough, the purpose of my answer was to provide more detail to my existing comments which extended beyond another comment in my opinion – Sayse Jul 23 '13 at 10:54
  • do you have any suggestions as to how i'm going to do that unit test? thanks – jbdeguzman Jul 23 '13 at 11:06
  • There is a link in this question that has a getting started guide.. basically just try to recreate the bug – Sayse Jul 23 '13 at 11:45
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One possible solution could be is using Web Worker and run your JS code inside it. After a while, if there is no any responce from it, call worker.terminate() to "kill" it.

Pay attention that web workers has strong limitations: for example you can not access UI element from within the code that runs in web worker scope, and it's not supported on old browsers.

I don't know if web worker is suitable in your case, but this one is option that may help.

Tigran
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  • I'll try this. Hopefully this is what I need. tnx! – jbdeguzman Jul 23 '13 at 10:25
  • @jbdeguzman: sorry there was a typo in my asnwer: you *can not* access UI elements from JS code that runs on webworker. If this is still suitable for your case, go ahead and try if this solves your problem. – Tigran Jul 23 '13 at 10:27
  • i think it's still suitable. all i need is something to test if the js file works well or not without affecting my page and still allowing me to use the controls. if it does, i'll run it on my page. if not, i will just ignore the file. i'll try it now. – jbdeguzman Jul 23 '13 at 10:36
  • w=new Worker(“demo_workers.js”); -->this part doesn't work on my version of Chrome. I don't know why. If it's IE i would understand. – jbdeguzman Jul 23 '13 at 11:22
  • i have the latest version of Chrome (Version 28.0.1500.72). and according to that source, it works on any version of chrome. i just copied code from http://www.w3schools.com/html/html5_webworkers.asp and i don't know why it still does not work in chrome. only in Mozilla and safari. – jbdeguzman Jul 23 '13 at 11:38
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Use debugger; to debug the script file. Put debugger; symbol beginning of the script's method which will be executed and run in chrome (since it is easy to debug) . click F12 to switch on the debugger tool. The script execution will stop on the line you put the debugger; and debug it line by line.

If the script is executing an infinite loop the chrome tab will crash with a message "Aw, Snap!". You can refer the call stack to find the method causing problem.

Aneesh Mohan
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  • i don't want to know what/where the problem is. I want to be able to handle an occurrence of infinite loop within a js file regardless of its cause. I need to avoid my page to hang. – jbdeguzman Jul 23 '13 at 10:32
  • @jbdeguzman may be `throw ""`; will do the job. `setTimeOut(function(){ throw ""; },delay);` that will avoid the hanging of the page and will stop script execution. – Aneesh Mohan Jul 23 '13 at 10:37
  • when the script has infinite loop, the page hangs. and when the page hangs, it will not do anything anymore. even if the delay on the setTimeout has passed, the function with throw will not be executed. – jbdeguzman Jul 23 '13 at 11:05