[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

One possibility is matching the .toString result against a regexp to get the function body, and then trim to check whether it has become an empty string:

var f = function foo()    { 


};

/^function [^(]*\(\)[ ]*{(.*)}$/.exec(
     f.toString().replace(/\n/g, "")
)[1].trim() === ""; // true

That ugly regexp does take care of spaces aroung named functions as well as extraneous spaces before the name and the opening brace. Spaces like in foo () do seem to be removed, so there is no reason to check for those.