The Reflect.set()
static method is like the property accessor and assignment syntax, but as a function.
The Reflect.set()
static method is like the property accessor and assignment syntax, but as a function.
Reflect.set(target, propertyKey, value) Reflect.set(target, propertyKey, value, receiver)
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 for propertyKey
on target
. If provided and target
does not have a setter for propertyKey
, the property will be set on receiver
instead.
A Boolean
indicating whether or not setting the property was successful.
TypeError
Thrown if target
is not an object.
Reflect.set()
provides the reflective semantic of a property access. That is, Reflect.set(target, propertyKey, value, receiver)
is semantically equivalent to:
target[propertyKey] = value;
Note that in a normal property access, target
and receiver
would observably be the same object.
Reflect.set()
invokes the [[Set]]
object internal method of target
.
// Object const obj = {}; Reflect.set(obj, "prop", "value"); // true obj.prop; // "value" // Array const 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". Reflect.set(obj); // true Reflect.getOwnPropertyDescriptor(obj, "undefined"); // { value: undefined, writable: true, enumerable: true, configurable: true }
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 }
Specification |
---|
ECMAScript Language Specification # sec-reflect.set |
Desktop | Mobile | Server | ||||||||||||
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Chrome | Edge | Firefox | Opera | Safari | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | WebView Android | Deno | Node.js | ||
set |
49 | 12 | 42 | 36 | 10 | 49 | 42 | 36 | 10 | 5.0 | 49 | 1.0 | 6.0.0 |
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https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/set