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Strict equality (===)

The strict equality operator (===) checks whether its two operands are equal, returning a Boolean result. Unlike the equality operator, the strict equality operator always considers operands of different types to be different.

Try it

Syntax

x === y

Description

The strict equality operators (=== and !==) provide the IsStrictlyEqual semantic.

  • If the operands are of different types, return false.
  • If both operands are objects, return true only if they refer to the same object.
  • If both operands are null or both operands are undefined, return true.
  • If either operand is NaN, return false.
  • Otherwise, compare the two operand's values:
    • Numbers must have the same numeric values. +0 and -0 are considered to be the same value.
    • Strings must have the same characters in the same order.
    • Booleans must be both true or both false.

The most notable difference between this operator and the equality (==) operator is that if the operands are of different types, the == operator attempts to convert them to the same type before comparing.

Examples

Comparing operands of the same type

console.log("hello" === "hello");   // true
console.log("hello" === "hola");    // false

console.log(3 === 3);               // true
console.log(3 === 4);               // false

console.log(true === true);         // true
console.log(true === false);        // false

console.log(null === null);         // true

Comparing operands of different types

console.log("3" === 3);           // false

console.log(true === 1);          // false

console.log(null === undefined);  // false

Comparing objects

const object1 = {
  name: "hello"
}

const object2 = {
  name: "hello"
}

console.log(object1 === object2);  // false
console.log(object1 === object1);  // true

Specifications

Browser compatibility

Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet Deno Node.js
Strict_equality
1
12
1
4
4
1
4.4
18
4
10.1
1
1.0
1.0
0.10.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Strict_equality