Questa traduzione è incompleta. Collabora alla traduzione di questo articolo dall’originale in lingua inglese.

Il metodo Object.is() determina se i due parametri di input hanno lo stesso valore.

Syntax

Object.is(value1, value2);

Parametri

value1
Il primo valore da comparare.
value2
Il secondo valore da comparare.

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

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support30 Yes22 No Yes9
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support Yes Yes Yes22 No Yes9

See also

Tag del documento e collaboratori

 Hanno collaborato alla realizzazione di questa pagina: Rawnly
 Ultima modifica di: Rawnly,