Object.prototype.constructor

The constructor data property of an Object instance returns a reference to the constructor function that created the instance object. Note that the value of this property is a reference to the function itself, not a string containing the function's name.

Note: This is a property of JavaScript objects. For the constructor method in classes, see its own reference page.

Value

A reference to the constructor function that created the instance object.

Note: This property is created by default on the prototype property of every constructor function and is inherited by all objects created by that constructor.

Description

Any object (with the exception of null prototype objects) will have a constructor property on its [[Prototype]]. Objects created with literals will also have a constructor property that points to the constructor type for that object — for example, array literals create Array objects, and object literals create plain objects.

const o1 = {};
o1.constructor === Object; // true

const o2 = new Object();
o2.constructor === Object; // true

const a1 = [];
a1.constructor === Array; // true

const a2 = new Array();
a2.constructor === Array; // true

const n = 3;
n.constructor === Number; // true

Note that constructor usually comes from the constructor's prototype property. If you have a longer prototype chain, you can usually expect every object in the chain to have a constructor property.

const o = new TypeError(); // Inheritance: TypeError -> Error -> Object
const proto = Object.getPrototypeOf;
proto(o).constructor === TypeError; // true
proto(proto(o)).constructor === Error; // true
proto(proto(proto(o))).constructor === Object; // true