Object.is

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

Syntax

Object.is(value1, value2);

Parameters

value1The first value to compare.value2The 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
both the same object
both numbers and
- both +0
- both -0
- both NaN
- or both non-zero and both not NaN and both have the same value

This is not the same as being equal according 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.

This is also not the same as being equal according to the === operator. The === operator (and the == operator as well) treats the number values -0 and +0 as equal and treats Number.NaN as not equal to NaN.

Examples

Object.is('foo', 'foo');     // true
Object.is(window, window);   // true

Object.is('foo', 'bar');     // false
Object.is([], []);           // false

var test = { a: 1 };
Object.is(test, test);       // true

Object.is(null, null);       // true

// Special Cases
Object.is(0, -0);            // false
Object.is(-0, -0);           // true
Object.is(NaN, 0/0);         // true

Polyfill

if (!Object.is) {
  Object.is = function(x, y) {
    // SameValue algorithm
    if (x === y) { // Steps 1-5, 7-10
      // Steps 6.b-6.e: +0 != -0
      return x !== 0 || 1 / x === 1 / y;
    } else {
     // Step 6.a: NaN == NaN
     return x !== x && y !== y;
    }
  };
}

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262)The definition of 'Object.is' in that specification.	Standard	Initial definition.
ECMAScript Latest Draft (ECMA-262)The definition of 'Object.is' in that specification.	Living Standard

Browser compatibility

Feature	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari
Basic Support	30	(Yes)	22	No	(Yes)	9

Feature	Android	Chrome for Android	Edge mobile	Firefox for Android	IE mobile	Opera Android	iOS Safari
Basic Support	(Yes)	(Yes)	(Yes)	22	No	(Yes)	9