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 (meaning both values reference the same object in memory)
  • 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 only difference between Object.is() and === is in their treatment of signed zeroes and NaNs. For example, the === operator (and the == operator) treats the number values -0 and +0 as equal. Also, the === operator treats Number.NaN and NaN as not equal.


Using Object.is

// Case 1: Evaluation result is the same as using ===
Object.is(25, 25);                // true
Object.is('foo', 'foo');          // true
Object.is('foo', 'bar');          // false
Object.is(null, null);            // true
Object.is(undefined, undefined);  // true
Object.is(window, window);        // true
Object.is([], []);                // false
const foo = { a: 1 };
const bar = { a: 1 };
Object.is(foo, foo);              // true
Object.is(foo, bar);              // false

// Case 2: Signed zero
Object.is(0, -0);                 // false
Object.is(+0, -0);                // false
Object.is(-0, -0);                // true
Object.is(0n, -0n);               // true

// Case 3: NaN
Object.is(NaN, 0/0);              // true
Object.is(NaN, Number.NaN)        // true


ECMAScript Language Specification
# sec-object.is

Browser compatibility

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See also