Inspired by Lammert Bies' CRC Calculation page, which I've used many many times for my work and projects, I decided to write the same with javascript and without the 800 char limit, and here it is. You can use it as you want. Here's the calculation source written in javascript. The magic happens in CRCMaster.Calculate() method.
Resources for CRC calculation (except from StackOverflow, and Google),