[OFF-TOPIC] JavaScript tool that helps find problems

Question

Somebody asked me to find some bug in their JavaScript... it was a spurious bug, which took a few of us quite a while to find.

I have found, that this tool would have found the problems:
http://jshint.com/

You copy and paste JavaScript code into it, and it gives you warnings about possible suspect code. Of course, it won't fix logic problems, but it can help us to spot issues, we might sometimes miss.

Answer 1

This can also be directly integrated to your code editor that supports plugins (sublime text, atom & co), they go by the name of linters (jslinter, phplinter...etc).

Answer 2

Top tip KINGDX! I used to use HTML and CSS validators at one point. These also helped. Tools can be so helpful in development!