Should I be removing console.log from production code?

Question

I currently have this JS statement everywhere in my code:

window.console && console.log("Foo"); 

I am wondering if this is costly at all, or has any negative side-effects in production.

Am I free to leave client-side logging in, or should it go?

EDIT: In the end, I suppose the best argument I (and anyone else?) can come up with is that there is a possibly non-negligible amount of extra data transferred between the server and the client by leaving logging messages left in. If production code is to be fully optimized, logging will have to be removed to reduce the size of javascript being sent to the client.

Answer 1

Another way of dealing with this is to 'stub' out the console object when it isn't defined so no errors are thrown in contexts that do not have the console i.e.

if (!window.console) {   var noOp = function(){}; // no-op function   console = {     log: noOp,     warn: noOp,     error: noOp   } } 

you get the idea... there are a lot of functions defined on the various implementations of the console, so you could stub them all or just the ones you use (e.g. if you only ever use console.log and never used console.profile, console.time etc...)

This for me is a better alternative in development than adding conditionals in front of every call, or not using them.

see also: Is it a bad idea to leave "console.log()" calls in your producton JavaScript code?

Answer 2

You should not add development tools to a production page.

To answer the other question: The code cannot have a negative side-effect:

• window.console will evaluate to false if console is not defined
• console.log("Foo") will print the message to the console when it's defined (provided that the page does not overwrite console.log by a non-function).