The handler.isExtensible()
method is a trap for Object.isExtensible()
.
handler.isExtensible()
Try it
Syntax
new Proxy(target, { isExtensible: function(target) { } });
Parameters
The following parameter is passed to the isExtensible()
method. this
is bound to the handler.
-
target
-
The target object.
Return value
The isExtensible()
method must return a boolean value.
Description
The handler.isExtensible()
method is a trap for Object.isExtensible()
.
Interceptions
This trap can intercept these operations:
Invariants
If the following invariants are violated, the proxy will throw a TypeError
:
-
Object.isExtensible(proxy)
must return the same value asObject.isExtensible(target)
.
Examples
Trapping of isExtensible
The following code traps Object.isExtensible()
.
const p = new Proxy({}, { isExtensible: function(target) { console.log('called'); return true; } }); console.log(Object.isExtensible(p)); // "called" // true
The following code violates the invariant.
const p = new Proxy({}, { isExtensible: function(target) { return false; } }); Object.isExtensible(p); // TypeError is thrown
Specifications
Specification |
---|
ECMAScript Language Specification # sec-proxy-object-internal-methods-and-internal-slots-isextensible |
Browser compatibility
Desktop | Mobile | Server | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | Deno | Node.js | |
isExtensible |
49
|
12
|
31
|
No
|
36
|
10
|
49
|
49
|
31
|
36
|
10
|
5.0
|
1.0
|
6.0.0
|
See also
© 2005–2022 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/isExtensible