The Object.is()
method determines whether two values are the same value.
Syntax
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 bothfalse
- 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
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
.
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; } }; }
Examples
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
Specifications
Specification |
---|
ECMAScript (ECMA-262) The definition of 'Object.is' in that specification. |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
is | Chrome Full support 30 | Edge Full support 12 | Firefox Full support 22 | IE No support No | Opera Full support 17 | Safari Full support 9 | WebView Android Full support ≤37 | Chrome Android Full support 30 | Firefox Android Full support 22 | Opera Android Full support 18 | Safari iOS Full support 9 | Samsung Internet Android Full support 2.0 | nodejs Full support 0.10 |
Legend
- Full support
- Full support
- No support
- No support
See also
- Equality comparisons and sameness — a comparison of all three built-in sameness facilities