Firebug, the ultimate javascript debugger for firefox, automatically creates a “console” object that has various methods that can be used to aid in debugging your javascript apps.

Full Documentation is here http://www.getfirebug.com/console.html

console.log() is the most used, with the ability to pass parameters and a formatted string.

One of the nice things is, if you log an object it displays all the objects properties as well.

For performance testing console.time(id) and console.timeEnd(id) are very useful.

consolt.trace() will even dump the full stack at the point it is called.

 

If you haven’t got firebug, it’s a must if you are developing with firefox.  Go get it here