JS: Reflect.construct

(new in ECMAScript 2015)

Reflect.construct(Fcon, [args])

same as new Fcon(args).

Fcon is a Constructor, args are arguments.

🟢 TIP: This function is similar to new (operator) but in a function form. Function form lets you manipulate expressions at run-time.

console.log(Reflect.construct(Date, []));
// 2026-02-07T18:12:17.671Z

console.log(Reflect.construct(Array, [3]));
// [ <3 empty items> ]

console.log(Reflect.construct(Map, [[[3, "n3"], [4, "n4"]]]));
// Map(2) { 3 => "n3", 4 => "n4" }

Reflect.construct(Fcon, [args], Fcon2)

• Use constructor Fcon to create an object with args, but use constructor Fcon2 to set the parent.

// prototype object
const proto1 = Object.create(Object.prototype);
proto1.kk = "this is proto1";

// constructor
function C1(x) {
  this.name = x;
}
C1.prototype = proto1;

// s------------------------------

// prototype object
const proto2 = Object.create(Object.prototype);
proto2.kk = "this is proto2";

// constructor
function C2(x) {
  this.name = x;
}
C2.prototype = proto2;

// s------------------------------

// create a object using constructor C1, but set prototype via constructor C2
const xj = Reflect.construct(C1, ["aa"], C2);

console.log(xj);
// { name: "aa" }

console.log(Reflect.getPrototypeOf(xj) === proto2);
// true