Bad idea to leave “console.log()” calls in your production JavaScript code?

It will cause Javascript errors, terminating the execution of the block of Javascript containing the error.

You could, however, define a dummy function that’s a no-op when Firebug is not active:

if(typeof console === "undefined") {
    console = { log: function() { } };
}

If you use any methods other than log, you would need to stub out those as well.