Object.is()

Object.is(value1, value2)

Returns: boolean · Updated March 16, 2026 · Object Methods

object comparison equality

Object.is() compares two values for strict equality with subtle differences from the === operator. Unlike ===, it treats NaN as equal to itself and distinguishes between positive and negative zeros. This method is particularly useful when you need exact equality semantics, such as in polyfills or when working with values that have special zero representations.

Syntax

Object.is(value1, value2)

Parameters

Parameter	Type	Default	Description
value1	any	—	First value to compare
value2	any	—	Second value to compare

Examples

Basic usage

Object.is(1, 1);
// true

Object.is(1, '1');
// false (different types)

Object.is(NaN, NaN);
// true (=== returns false)

Zero handling

Object.is(0, -0);
// false (=== returns true)

Object.is(-0, -0);
// true

Object.is(+0, +0);
// true

Object.is(0, 0);
// true

Object identity

const obj = {};
Object.is(obj, obj);
// true (same reference)

Object.is({}, {});
// false (different objects)

const arr = [Global_Objects::eval];
Object.is(arr, arr);
// true

Common Patterns

Use Object.is() when you need precise equality checking, especially when dealing with NaN comparisons or when the distinction between positive and negative zero matters:

// Safe NaN check (Number.isNaN also works, but Object.is works too)
function isNaN(value) {
  return Object.is(value, NaN);
}

// Checking for signed zero in physics calculations
function hasNegativeZero(n) {
  return Object.is(n, -0);
}

// Custom equality for libraries that need === semantics but with NaN handling
function deepEqual(a, b) {
  if (a === b) return true;
  if (Object.is(a, b)) return true;
  // ... more complex comparison
}