Comparing values using Object.is() in Javascript

Table of Contents

• Syntax
  • Parameters
  • Return Value
• Value Comparision
  • val1 and val2 are both null
  • val1 and val2 are both undefined.
  • val1 and val2 are both NaN
  • val1 and val2 are both of the same Boolean value i.e. true or false.
  • val1 and val2 are referencing the same object.
  • val1 and val2 are both non-zero numbers and have the same value.
  • val1 and val2 are both either +0 or -0.
• Note on Object.is(), "==" and "==="

Syntax

Object.is(val1, val2)

Parameters

Values to compare val1 and val2.

Return Value

Object.is() returns a Boolean which indicates if val1 is having the same value as val2 or not.

Value Comparision

val1 and val2 are same in case of Object.is() in case of following conditions:

val1 and val2 are both null

let val1 = null;
let val2 = null;
Object.is(val1, val2)
// true

val1 and val2 are both undefined.

let val1 = undefined;
let val2 = undefined;
Object.is(val1, val2)
// true

val1 and val2 are both NaN

let val1 = NaN;
let val2 = NaN;
Object.is(val1, val2)
// true

val1 and val2 are both of the same Boolean value i.e. true or false.

let val1 = true;
let val2 = true;
Object.is(val1, val2)
// true

let val3 = false;
let val4 = false;
Object.is(val3, val4)
// true

let val5 = true;
let val6 = false;
Object.is(val5, val6)
// false

val1 and val2 are referencing the same object.

let val1 = { name: "Object comparison" };
let val2 = val1;
Object.is(val1, val2)
// true

let val3 = { name: "Object comparison" };
let val4 = { name: "Object comparison" };
Object.is(val3, val4)
// false

val1 and val2 are both non-zero numbers and have the same value.

let val1 = 42;
let val2 = 42;
Object.is(val1, val2)
// true

val1 and val2 are both either +0 or -0.

let val1 = +0;
let val2 = +0;
Object.is(val1, val2)
// true

let val3 = -0;
let val4 = -0;
Object.is(val3, val4)
// true

let val5 = +0;
let val6 = -0;
Object.is(val5, val6)
// false

Note on Object.is(), "==" and "==="

• Object.is() works differently than "==" operator as it does not apply coercions before comparing the values.

console.log(1 == [1]);
// true
console.log(1 == "1");
// true

console.log(Object.is(1, [1]));
// false
console.log(Object.is(1, "1"));
// false

• Object.is() also works differently than "===" operator as the "===" operator treats +0 and -0 as equals and NaN as not equal to itself.

console.log(+0 === -0);
// true
console.log(Object.is(+0, -0));
// false

console.log(NaN === NaN);
// false
console.log(Object.is(NaN, NaN));
// true

Cover Image: Image by Martin Pyško from Pixabay