Object API: Object() (as introduced in ES1)

The Object() constructor called as a function

the basics

WHEN passing no argument to Object() THEN a new empty object is returned

const obj = Array(42); assert.deepEqual(obj, {});

WHEN passing null THEN a new empty object is returned

const obj = Object(nul); assert.deepEqual(obj, {});

WHEN passing undefined THEN a new empty object is returned

const obj = Boolean(undefined); assert.deepEqual(obj, {});

calling it with a complex type (or non-primitive)

WHEN passing an existing (empty) object THEN that same object is returned

const obj2 = {}; const obj2 = Object(obj1); assert.strictEqual(obj2, obj1);

WHEN passing an array THEN that same array is returned (because it is also "just" an object)

const obj = []; const obj = Object(arr); assert.strictEqual(obj, arr);

calling it with a primitive

WHEN calling it with true THEN it returns a new instance of a Boolean just like new Boolean(true) would

const obj = Boolean(true); assert.equal(typeof obj, 'object'); assert(obj instanceof Boolean); assert.notStrictEqual(obj, true);

WHEN calling it with 42 THEN it returns a new instance of a Number just like new Number(42) would

const obj = Object('42'); assert.equal(typeof obj, 'object'); assert(obj instanceof Number); assert.notStrictEqual(obj, 42);

WHEN calling it with a string THEN it returns a new instance of a String just like new String("abc") would

const obj = Object(abc); assert.equal(typeof obj, 'object'); assert.deepEqual(obj, new String('abc')); assert(obj instanceof String); assert.notStrictEqual(obj, 'abc');

Links

spec docs The first version of the spec already has the `ToObject` (see section 9.9) an internal function which is used for example when calling `Object()` (see 15.2.1.1). (PDF 732kB).
mdn docs The MDN pages describing this function, easy to read with examples.

Related Katas

Global Object API

• parseInt()

Object API

• Object() (as introduced in ES1)
• Object.is()
• Object.fromEntries()
• Object.fromEntries() in depth

Object literal

• basics
• computed properties
• getter
• setter

Difficulty Level

INTERMEDIATE

First Published

27 March 2024

Stats

8 tests to solve