[JavaScript] Strict inequality (!==)

Strict inequality (!==)

The strict inequality operator (!==) checks whether its two operands are not equal, returning a Boolean result. Unlike the inequality operator, the strict inequality operator always considers operands of different types to be different.

Syntax

x !== y

Copy to Clipboard

Description

The strict inequality operator checks whether its operands are not equal. It is the negation of the strict equality operator so the following two lines will always give the same result:

x !== y

!(x === y)

Copy to Clipboard

For details of the comparison algorithm, see the page for the strict equality operator.

Like the strict equality operator, the strict inequality operator will always consider operands of different types to be different:

3 !== "3"; // true

Copy to Clipboard

Examples

Comparing operands of the same type

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

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

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

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

Copy to Clipboard

Comparing operands of different types

console.log("3" !== 3);           // true

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

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

Copy to Clipboard

Comparing objects

const object1 = {
  name: "hello"
}

const object2 = {
  name: "hello"
}

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

Copy to Clipboard

Specifications

Specification

ECMAScript Language Specification # sec-equality-operators