Strict inequality (!==) - JavaScript 编辑

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.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Syntax

x !== y

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)

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

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

Comparing operands of different types

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

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

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

Comparing objects

const object1 = {
  name: "hello"
}

const object2 = {
  name: "hello"
}

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

Specifications

Specification
ECMAScript (ECMA-262) The definition of 'Equality operators' in that specification.

Browser compatibility

BCD tables only load in the browser

See also

• Equality operator
• Inequality operator
• Strict equality operator