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


Object.is(value1, value2);


The first value to compare.
The second value to compare.

Return value

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


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 (means both object have same reference)
  • 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.


if (!Object.is) {
  Object.defineProperty(Object, "is", {
    value: 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;


Using Object.is

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

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

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

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

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


ECMAScript (ECMA-262)
The definition of 'Object.is' in that specification.

Browser compatibility

Update compatibility data on GitHub
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
isChrome Full support 30Edge Full support 12Firefox Full support 22IE No support NoOpera Full support 17Safari Full support 9WebView Android Full support ≤37Chrome Android Full support 30Firefox Android Full support 22Opera Android Full support 18Safari iOS Full support 9Samsung Internet Android Full support 2.0nodejs Full support 0.10


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See also