Function.caller

The function.caller property returns the function that invoked the specified function.

Description

If the function f was invoked by the top level code, the value of f.caller is null, otherwise it's the function that called f.

This property replaces the obsolete arguments.caller property of the arguments object.

The special property __caller__, which returned the activation object of the caller thus allowing to reconstruct the stack, was removed for security reasons.

Notes

Note that in case of recursion, you can't reconstruct the call stack using this property. Consider:

function f(n) { g(n - 1); }
function g(n) { if (n > 0) { f(n); } else { stop(); } }
f(2);

At the moment stop() is called the call stack will be:

f(2) -> g(1) -> f(1) -> g(0) -> stop()

The following is true:

stop.caller === g && f.caller === g && g.caller === f

so if you tried to get the stack trace in the stop() function like this:

var f = stop;
var stack = 'Stack trace:';
while (f) {
  stack += '\n' + f.name;
  f = f.caller;
}

the loop would never stop.

Examples

Checking the value of a function's caller property

The following code checks the value a function's caller property.

function myFunc() {
  if (myFunc.caller == null) {
    return 'The function was called from the top!';
  } else {
    return 'This function\'s caller was ' + myFunc.caller;
  }
}

Specifications

Not part of any specification. Implemented in JavaScript 1.5.

Browser compatibility

See also

• Implementation bug for SpiderMonkey bug 65683