W3cubDocs

Errors: Deprecated caller or arguments usage

Message

Warning: ReferenceError: deprecated caller usage (Firefox)
Warning: ReferenceError: deprecated arguments usage (Firefox)
TypeError: 'callee' and 'caller' cannot be accessed in strict mode. (Safari)

Error type

A strict-mode-only warning that a ReferenceError occurred. JavaScript execution won't be halted.

What went wrong?

In strict mode, the Function.caller or Function.arguments properties are used and shouldn't be. They are deprecated, because they leak the function caller, are non-standard, hard to optimize and potentially a performance-harmful feature.

Examples

Deprecated `function.caller` or `arguments.callee.caller`

Function.caller and arguments.callee.caller are deprecated (see the reference articles for more information).

'use strict';

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

myFunc();
// Warning: ReferenceError: deprecated caller usage
// "The function was called from the top!"

`Function.arguments`

Function.arguments is deprecated (see the reference article for more information).

'use strict';

function f(n) { g(n - 1); }

function g(n) {
  console.log('before: ' + g.arguments[0]);
  if (n > 0) { f(n); }
  console.log('after: ' + g.arguments[0]);
}

f(2);

console.log('returned: ' + g.arguments);
// Warning: ReferenceError: deprecated arguments usage