Before Firebug, there was Venkman[0] which was definitely shite but worked if you had enough courage to understand its byzantine behavior. It provided a profiler on top of the JS debugger.
And IE development could use Visual Studio (and later Visual Studio Express web edition) for a slightly better experience than the MS Script Debugger, although the core issues such as not being able to see let alone debug toplevel javascript remained).
It admittedly had a learning curve roughly on-part with Eclipse over POTS with a drunk monkey at the other end of the call. I was rather happy when Firebug came into my world.
And IE development could use Visual Studio (and later Visual Studio Express web edition) for a slightly better experience than the MS Script Debugger, although the core issues such as not being able to see let alone debug toplevel javascript remained).
[0] https://developer.mozilla.org/en-US/docs/Venkman_Introductio...