How to find out where a function is called from in JavaScript?

Question

Is it possible to find out where a function is called from? If yes, then how to detect, if a function is called from a global scope, from another function, or perhaps from a browser console?

Take a look at the following example:

<script>
    function myFunc1() {
        // some code
        myFunc2(); // I was called from myFunc1()
    }
    function myFunc2() {
        var callerName = new String;
        callerName = arguments.callee.caller.name;
        // some code
        alert('I was called from ' + callerName + ' function');
    }
    myFunc2(); // I was called from global scope
</script>

I know that this line callerName = arguments.callee.caller.name;in the example above, would give me caller function's name. But I don't know how to detect if a function was called from a global scope. For instance if I change myFunc2() and add an if else statement to check if arguments.callee.caller.name returns an undefined value, knowing that this will happen, when a function is called from a global scope:

myFunc2() {
var callerName = new String;
callerName = arguments.callee.caller.name;
    if(callerName == undefined) {
        alert('I was called from global scope');
    } else {
        alert('I was called from ' + callerName + ' function');
    }
}

However, this will not work if myFunc2() is called from a global scope and callerName = arguments.callee.caller.name; will cause JavaScript to throw the following error:

TypeError: 'null' is not an object (evaluating 'arguments.callee.caller.name')

So I am back to square one, and the question still remains:

• How to detect if a function is called from a global scope?
• If it's called from a global scope, is it from a browser console?

Answer 1

In Chrome, you can use:

console.trace(); 

Just add that line in your function, I usually place it as the first line. If you view the console you'll see the name of your function, and below that line you'll see where it's being called from.

Answer 2

If the function is called from the global scope, arguments.callee.caller.name will be undefined. Otherwise, it will be the name of the caller function (which also represents the scope it was called from).

So what you already have should work, except in strict mode, where arguments.callee is not available.

---

Additionaly: the developer tools available from your browser are probably a better way to inspect this kind of thing: just set a breakpoint and look at the stack trace panel. Unless of course your code itself needs to know the calling scope at runtime.