Object.is()

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

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Syntax

js
Object.is(value1, value2)

Parameters

value1

The first value to compare.

value2

The second value to compare.

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:

  • both undefined

  • both null

  • both true or both false

  • both strings of the same length with the same characters in the same order

  • both the same object (meaning both values reference the same object in memory)

  • both BigInts with the same numeric value

  • both symbols that reference the same symbol value

  • both numbers and

    • both +0
    • both -0
    • both NaN
    • or both non-zero, not NaN, and have the same value

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()

js
// 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

Specification
ECMAScript Language Specification
# sec-object.is

Browser compatibility

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See also