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.
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
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | 1.0 (1.7 or earlier) | 8.0 | (Yes) | (Yes) |
Feature | Android | Chrome for Android | Edge | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|---|
Basic support | (Yes) | (Yes) | (Yes) | 1.0 (1.0) | (Yes) | (Yes) | (Yes) |
See also
- Implementation bug for SpiderMonkey bug 65683