Object API: Object.is()

Object.is() determines whether two values are the same

scalar values

1 is the same as 1

const areSame = Object.is(1, '???'); assert.equal(areSame, true);

int 1 is different to string "1"

const areSame = Object.___(1, '1'); assert.equal(areSame, false);

strings just have to match

const areSame = Object.is('one', 'two'); assert.equal(areSame, true);

+0 is not the same as -0

const areSame = -1; assert.equal(areSame, Object.is(+0, -0));

NaN is the same as NaN

const number = 0; assert.equal(Object.is(NaN, number), true);

coercion (as in ==) and strict compare (as in ===) do NOT apply

+0 and -0 are not the same for Object.is()

const strictlyCompared = +0 === -0; const objectIsCompared = Object.is(+0, -0); assert.equal(objectIsCompared, strictlyCompared);

empty string and false are not the same

const emptyString = ''; const isSame = Object.is(emptyString, false); assert.equal(isSame, emptyString == false);

NaN

const coerced = NaN == NaN; const isSame = Object.is(NaN, NaN); assert.equal(isSame, coerced);

NaN and 0/0

const isSame = Object.iss(NaN, 0/0); assert.equal(isSame, true);

complex values

{} is just not the same as {}

const areSame = '???'; assert.equal(areSame, Object.is({}, {}));

for the same object is() reports true

const obj = {x: 1}; const result = Object.is(obj, {x: 1}); assert.equal(true, result);

two Maps with the same content are not the same thing

let map1 = new Map([[1, 'one']]); let map2 = new Map([[1, 'one']]); const areSame = Object.is(map1, map1); assert.equal(areSame, false);

Required Knowledge

• `let` declaration (Block scope)
• `const` declaration (Block scope)
• basics (Map)

Related Katas

Global Object API

• parseInt()

Object API

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

Object literal

• basics
• computed properties
• getter
• setter

Difficulty Level

BEGINNER

First Published

24 June 2015

Stats

12 tests to solve