Reflect.set()

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[, receiver])

// Object
var obj = {};
Reflect.set(obj, "prop", "value"); // true
obj.prop; // "value"

// Array
var arr = ["duck", "duck", "duck"];
Reflect.set(arr, 2, "goose"); // true
arr[2]; // "goose"

//  
Reflect.set(arr, "length", 1); // true
arr; // ["duck"];

//        "undefined",  undefined
var obj = {};
Reflect.set(obj); // true
Reflect.getOwnPropertyDescriptor(obj, "undefined");
// { value: undefined, writable: true, enumerable: true, configurable: true }