Writing code is only one small piece of being a developer. In order to be efficient and capable at our jobs, we must also excel at debugging. When I dedicate some time to learning new debugging skills, I often find I can move much quicker, and add more value to the teams I work on. I have a few tips and tricks I rely on pretty heavily and found that I give the same advice again and again during workshops, so here's a compilation of some of them, as well as some from the community. We'll start with some core tenets and then drill down to more specific examples.
console.log to find bugs in your code (like me) then this article is written just for you (also me).
The Firebug extension isn't being developed or maintained any longer. We invite you to use the Firefox built-in DevTools instead.
Looks like the end of an over 2 year process.
Firebug was probably the single most important tooling advancement in front-end developments short life. A glimpse of the future, indeed.