Function.caller

Non-standard
This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

Summary

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

Example: 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

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support (Yes) 1.0 (1.7 or earlier) (Yes) (Yes) (Yes)
Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
Basic support (Yes) (Yes) 1.0 (1.0) (Yes) (Yes) (Yes)

See also

Document Tags and Contributors

Last updated by: fscholz,