严格不相等 (!==)

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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

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)
Equality operators

Browser compatibility

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DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Strict inequality (a !== b)Chrome Full support 1Edge Full support 12Firefox Full support 1IE Full support 4Opera Full support 4Safari Full support 1WebView Android Full support 1Chrome Android Full support 18Firefox Android Full support 4Opera Android Full support 10.1Safari iOS Full support 1Samsung Internet Android Full support 1.0nodejs Full support 0.1.100

Legend

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See also