Lately I needed to parse format that Cisco uses for specifying transfer masks and route patterns to an array of telephone numbers a user could choose from. I wrote a neat javascript function that traverses the string and does what needed. I even wrote a neat recursive function that displayed the numbers in HTML select field.

All worked fine. Until someone decided to test the thing on VM running Windows XP SP3 with IE 8.0.6001.18702 . The thing crashed. Not only that, it also displayed a nice little pop-up claiming that Javascript is running slow. We all know that really means you have an infinite loop somewhere in JS code. Thing is, I ran the code numerous times on my PC, which runs Windows XP SP3 and IE 8.0.6001.18702 as well. The only difference that my PC is not  a virtual machine. And it worked without a glitch. So I tested it to death in VMs IE and eventually located the problem.

Remember how you traversed a string in C? Typically you wrote something like this (and yes, I know I probably should have used a pointer):

As far as I remember, I use that all the time in JavaScript as well. I never had any issues. Guess what? In IE on VM that was the cause of my problems. So, all I had to do was:

And the stuff magically started to work.