In JavaScript, null is a primitive value that represents the intentional absence of any object value. It is often used to explicitly represent the absence of a value.
Additionally, there is also the undefined value, which represents a variable or property that has been declared but has not been assigned a value. While both null and undefined are falsy values in JavaScript, they have different use cases.
To assign a variable or property to the null value, you can use the following syntax:
let myVar = null;
To check if a value is null, you can use a strict equality comparison (===) with the null value:
if (myVar === null) {
// do something
}
You can also check if a value is null or undefined using a non-strict equality comparison (==):
if (myVar == null) {
// do something
}
However, it’s generally recommended to use strict equality comparisons (=== and !==) in JavaScript to avoid the unexpected types of coercion.
Type of null in JavaScript example
A simple example use the null value in JavaScript:
<!DOCTYPE html>
<html>
<body>
<script>
let myVar = null;
console.log(myVar);
if (myVar === null) {
console.log("myVar is null");
}
if (myVar == null) {
console.log("myVar is null or undefined");
}
</script>
</body>
</html>
Output:
Here are some examples to illustrate the difference between null and undefined in JavaScript:
let myVar1 = null; // value null
let myVar2; // undefined
console.log(myVar1); // null
console.log(myVar2); // undefined
console.log(myVar1 == null); //true (null is equal to undefined only in non-strict equality comparisons)
console.log(myVar2 == null); // false
console.log(myVar2 == undefined); //true (undefined is equal to null only in non-strict equality comparisons)Comment if you have any doubts or suggestions on this JS null topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version