Prevent Javascript from Stopping when Error is Encountered

Question

Our product inserts a script into client's websites, kind of like a live chat box.

Often, clients' websites have buggy javascript that also stops our code (the browser stops execution when errors are encountered). Is there any way to make our code still execute even though there are errors in the console about things like undefined methods or variables?

Thanks for your help.

Answer 1

The short answer is that you really can't.

"Solution" #1: You could insist that YOUR 3rd party code run before anyone else's. In most cases, this isn't possible or even desirable.

"Solution" #2: You could insist that the 1st party engineers wrap all 3rd party code in try/catch blocks. But, this solution really doesn't buy you any guarantee, because very frequently 3rd party libraries attach additional <script> tags to the page - these would not fall under the "jurisdiction" of the try/catch scope enclosing the code which created this/these tag(s).

"Solution" #3: You could build YOUR app entirely within the scope of an <iframe>, thereby avoiding the issue entirely. Unfortunately, even if you're very smart, you'll quickly run into cross domain violations, 3rd party cookie restrictions, and the like. It's very probable that this will not work for you.

"Solution" #4: You could explain the issue to your client, and have them demand that the other 3rd party code run cleanly. I say this is a "solution" because, frankly, it's not a "solution" to your question if your question is how to avoid doing exactly this.

Unfortunately, option #4 is your best bet. It may help if you observe other 3rd party libraries "breaking" in the same fashion: you can tell your client "hey, it's not just me - X, Y, and Z are all also 'broken' because of <name of other 3rd party library>." It may cause them to put the heat on the offending code, which makes the web a happier place for all involved.

Answer 2

As others have said, continuing after an error might not be the best thing to do but you can try this:

function ignoreerror()
{
   return true
}
window.onerror=ignoreerror();

More details here

The onerror event fires whenever an JavaScript error occurs (depending on your browser configuration, you may see an error dialog pop up). The onerror event is attached to the window object, a rather unusual place to take refuge in, but for good reason. It is attached this way so it can monitor all JavaScript errors on a page, even those in the section of the page.

Opera has a page with more details

Browsers supporting window.onerror
Chrome 13+
Firefox 6.0+
Internet Explorer 5.5+
Opera 11.60+
Safari 5.1+