UNB/ CS/ David Bremner/ teaching/ cs2613/ books/ mdn/ Reference/ Global Objects/ Object/ Object.is()

The Object.is() static method determines whether two values are the same value.

Syntax

Object.is(value1, value2)

Parameters

Return value

A boolean indicating whether or not the two arguments are the same value.

Description

Object.is() determines whether two values are the same value. Two values are the same if one of the following holds:

Object.is() is not equivalent to the == operator. The == operator applies various coercions to both sides (if they are not the same type) before testing for equality (resulting in such behavior as "" == false being true), but Object.is() doesn't coerce either value.

Object.is() is also not equivalent to the === operator. The only difference between Object.is() and === is in their treatment of signed zeros and NaN values. The === operator (and the == operator) treats the number values -0 and +0 as equal, but treats NaN as not equal to each other.

Examples

Using Object.is()

// Case 1: Evaluation result is the same as using ===
Object.is(25, 25); // true
Object.is("foo", "foo"); // true
Object.is("foo", "bar"); // false
Object.is(null, null); // true
Object.is(undefined, undefined); // true
Object.is(window, window); // true
Object.is([], []); // false
const foo = { a: 1 };
const bar = { a: 1 };
const sameFoo = foo;
Object.is(foo, foo); // true
Object.is(foo, bar); // false
Object.is(foo, sameFoo); // true

// Case 2: Signed zero
Object.is(0, -0); // false
Object.is(+0, -0); // false
Object.is(-0, -0); // true

// Case 3: NaN
Object.is(NaN, 0 / 0); // true
Object.is(NaN, Number.NaN); // true

Specifications

Browser compatibility

See also