As a backend developer, I don't get to work with JavaScript much anymore. However, from time to time, a project would come along that uses JavaScript (specifically, AJAX) to load some backend data on the fly. Of course, nothing works 100% right away*, so I would often have to tweak this JavaScript and massage it until it does what I need.
Here's where Firebug comes in with its JavaScript debugger. I'm used to using a debugger in every language I deal with, so using Firebug is a no brainer. Since it supports breakpoints, stopping execution and inspecting local variables and the rest of the scope generally beats alerts and console.logs for me.
Here's what a typical breakpoint looks …