Strict inequality (!==)
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
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.
Try it
console.log(1 !== 1);
// Expected output: false
console.log("hello" !== "hello");
// Expected output: false
console.log("1" !== 1);
// Expected output: true
console.log(0 !== false);
// Expected output: true
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
"hello" !== "hello"; // false
"hello" !== "hola"; // true
3 !== 3; // false
3 !== 4; // true
true !== true; // false
true !== false; // true
null !== null; // false
Comparing operands of different types
"3" !== 3; // true
true !== 1; // true
null !== undefined; // true
Comparing objects
const object1 = {
key: "value",
};
const object2 = {
key: "value",
};
console.log(object1 !== object2); // true
console.log(object1 !== object1); // false
Specifications
| Specification |
|---|
| ECMAScript® 2027 Language Specification # sec-equality-operators |
Browser compatibility
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Strict inequality (
a !== b)
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