Reflect.isExtensible()
The static Reflect
.isExtensible()
method determines if an object is extensible (whether it can have new properties added to it). It is similar to Object.isExtensible()
, but with some differences.
Syntax
Reflect.isExtensible(target)
Parameters
target
- The target object which to check if it is extensible.
Return value
A Boolean
indicating whether or not the target is extensible.
Exceptions
A TypeError
, if target
is not an Object
.
Description
The Reflect.isExtensible
method allows you determine if an object is extensible (whether it can have new properties added to it). It is the same method as Object.isExtensible()
.
Examples
Using Reflect.isExtensible()
See also Object.isExtensible()
.
// New objects are extensible. var empty = {}; Reflect.isExtensible(empty); // === true // ...but that can be changed. Reflect.preventExtensions(empty); Reflect.isExtensible(empty); // === false // Sealed objects are by definition non-extensible. var sealed = Object.seal({}); Reflect.isExtensible(sealed); // === false // Frozen objects are also by definition non-extensible. var frozen = Object.freeze({}); Reflect.isExtensible(frozen); // === false
Difference to Object.isExtensible()
If the first argument to this method is not an object (a primitive), then it will cause a TypeError
. With Object.isExtensible()
, a non-object first argument will be coerced to an object at first.
Reflect.isExtensible(1); // TypeError: 1 is not an object Object.isExtensible(1); // false
Specifications
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Reflect.isExtensible' in that specification. |
Standard | Initial definition. |
ECMAScript 2017 Draft (ECMA-262) The definition of 'Reflect.isExtensible' in that specification. |
Draft |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 49 | 42 (42) | No support | No support | No support |
Feature | Android | Chrome for Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|---|
Basic support | No support | No support | 42.0 (42) | No support | No support | No support |
See also
License
© 2016 Mozilla 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/reflect/isextensible