[removed] is given function empty?

Question

Let\'s have a function call

function doSomethingAndInvokeCallback(callback){
    // do something
    callback();
}

I can check if given arg

Answer 1

You might be able to get this from .toString():

var blank = function(){};
var f = function(){};
var f2 = function() { return 1; };

f.toString() == blank.toString(); // true
f2.toString() == blank.toString(); // false

but this is really prone to error:

var blank = function(){};
var f = function(){ }; // extra space!
f.toString() == blank.toString(); // false

You could munge the strings a bit to try to overcome this, but I suspect this is very browser-dependent. I wouldn't actually try to do this in a production environment if I were you. Even if you normalize the whitespace, it still won't catch other no-op lines, including comments, useless var statements, etc. To actually address these issues, you'd probably need a whole tokenizer system (or a crazy regex).