Reflect.set()
The static Reflect.set()
method works like setting a
property on an object.
Try it
Syntax
Reflect.set(target, propertyKey, value)
Reflect.set(target, propertyKey, value, receiver)
Parameters
target
-
The target object on which to set the property.
propertyKey
-
The name of the property to set.
value
-
The value to set.
receiver
Optional-
The value of
this
provided for the call to the setter forpropertyKey
ontarget
. If provided andtarget
does not have a setter forpropertyKey
, the property will be set onreceiver
instead.
Return value
A Boolean
indicating whether or not setting the property was successful.
Exceptions
Description
The Reflect.set
method allows you to set a property on an object. It does
property assignment and is like the
property accessor syntax as a function.
Examples
Using Reflect.set()
// Object
let obj = {}
Reflect.set(obj, 'prop', 'value') // true
obj.prop // "value"
// Array
let arr = ['duck', 'duck', 'duck']
Reflect.set(arr, 2, 'goose') // true
arr[2] // "goose"
// It can truncate an array.
Reflect.set(arr, 'length', 1) // true
arr // ["duck"]
// With just one argument, propertyKey and value are "undefined".
let obj = {}
Reflect.set(obj) // true
Reflect.getOwnPropertyDescriptor(obj, 'undefined')
// { value: undefined, writable: true, enumerable: true, configurable: true }
Different target and receiver
When the target
and receiver
are different, Reflect.set
will use the property descriptor of target
(to find the setter or determine if the property is writable), but set the property on receiver
.
const target = {};
const receiver = {};
Reflect.set(target, "a", 2, receiver); // true
// target is {}; receiver is { a: 2 }
const target = { a: 1 };
const receiver = {};
Reflect.set(target, "a", 2, receiver); // true
// target is { a: 1 }; receiver is { a: 2 }
const target = { set a(v) { this.b = v; } };
const receiver = {};
Reflect.set(target, "a", 2, receiver); // true
// target is { a: [Setter] }; receiver is { b: 2 }
Specifications
Specification |
---|
ECMAScript Language Specification # sec-reflect.set |
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