Baseline Widely available
The Reflect.set() static method is like the property accessor and assignment syntax, but as a function.
const object1 = {};
Reflect.set(object1, "property1", 42);
console.log(object1.property1);
// Expected output: 42
const array1 = ["duck", "duck", "duck"];
Reflect.set(array1, 2, "goose");
console.log(array1[2]);
// Expected output: "goose"
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 }
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