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

Question

I have a bunch of console.log() calls in my JavaScript.

Should I comment them out before I deploy to production?

I'd like to just leave them there, so I don't have to go to the trouble of re-adding the comments later on if I need to do any more debugging. Is this a bad idea?

Answer 1

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.

Answer 2

As others have already pointed it, leaving it in will cause errors in some browsers, but those errors can be worked around by putting in some stubs.

However, I would not only comment them out, but outright remove those lines. It just seems sloppy to do otherwise. Perhaps I'm being pedantic, but I don't think that "production" code should include "debug" code at all, even in commented form. If you leave comments in at all, those comments should describe what the code is doing, or the reasoning behind it--not blocks of disabled code. (Although, most comments should be removed automatically by your minification process. You are minimizing, right?)

Also, in several years of working with JavaScript, I can't recall ever coming back to a function and saying "Gee, I wish I'd left those console.logs in place here!" In general, when I am "done" with working on a function, and later have to come back to it, I'm coming back to fix some other problem. Whatever that new problem is, if the console.logs from a previous round of work could have been helpful, then I'd have spotted the problem the first time. In other words, if I come back to something, I'm not likely to need exactly the same debug information as I needed on previous occasions.

Just my two cents... Good luck!