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

console.log(1 === 1);
// Expected output: true

console.log("hello" === "hello");
// Expected output: true

console.log("1" === 1);
// Expected output: false

console.log(0 === false);
// Expected output: false

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

undefined

Comparing operands of the same type

"hello" === "hello"; // true
"hello" === "hola"; // false

3 === 3; // true
3 === 4; // false

true === true; // true
true === false; // false

null === null; // true

Comparing operands of different types

"3" === 3; // false
true === 1; // false
null === undefined; // false
3 === new Number(3); // false

Comparing objects

const object1 = {
  key: "value",
};

const object2 = {
  key: "value",
};

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

Specifications

ECMAScript® 2027 Language Specification