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    Object.is()

    This is a new technology, part of the ECMAScript 2015 (ES6) standard .
    This technology's specification has been finalized, but check the compatibility table for usage and implementation status in various browsers.

    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 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 for non-ES6 browsers

    Object.is() is a proposed addition to the ECMA-262 standard; as such it may not be present in all browsers. You can work around this by using the following code at the beginning of your scripts. This will allow you to use Object.is() when there is no built–in support.

    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.

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
    Basic support 30.0.1599.114 22 (22) Not supported (Yes) Not supported
    Feature Android Chrome for Android Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile
    Basic support Not supported ? 22.0 (22) Not supported Not supported Not supported

    See also

    Document Tags and Contributors

    Last updated by: Sheppy,