The static Reflect.preventExtensions()
method prevents new properties from ever being added to an object (i.e., prevents future extensions to the object). It is similar to Object.preventExtensions()
, but with some differences.
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Syntax
Reflect.preventExtensions(target)
Parameters
target
- The target object on which to prevent extensions.
Return value
A Boolean
indicating whether or not the target was successfully set to prevent extensions.
Exceptions
A TypeError
, if target
is not an Object
.
Description
The Reflect.preventExtensions()
method allows you to prevent new properties from ever being added to an object (i.e., prevents future extensions to the object). It is similar to Object.preventExtensions()
.
Examples
Using Reflect.preventExtensions()
See also Object.preventExtensions()
.
// Objects are extensible by default. let empty = {} Reflect.isExtensible(empty) // === true // ...but that can be changed. Reflect.preventExtensions(empty) Reflect.isExtensible(empty) // === false
Difference from Object.preventExtensions()
If the target
argument to this method is not an object (a primitive), then it will cause a TypeError
. With Object.preventExtensions()
, a non-object target
will be coerced to an object.
Reflect.preventExtensions(1) // TypeError: 1 is not an object Object.preventExtensions(1) // 1
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Reflect.preventExtensions' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
preventExtensions | Chrome Full support 49 | Edge Full support 12 | Firefox Full support 42 | IE No support No | Opera Full support 36 | Safari Full support 10 | WebView Android Full support 49 | Chrome Android Full support 49 | Firefox Android Full support 42 | Opera Android Full support 36 | Safari iOS Full support 10 | Samsung Internet Android Full support 5.0 | nodejs Full support 6.0.0 |
Legend
- Full support
- Full support
- No support
- No support