Difference Between Null and Undefined in JavaScript

In this article, we will learn about the difference between null and undefined in JavaScript. In JavaScript, null and undefined represent the absence of a value, but they have different meanings and use cases.

What is undefined in JavaScript?

It means a variable declared, but no value has been assigned to the variable. JavaScript automatically assigns undefined to uninitialized variables.

For example

Below is an example of undefined in javascript ?

var demo;
alert(demo); //shows undefined
alert(typeof demo); //shows undefined

Output

undefined
undefined

What is null in JavaScript?

null is an intentional absence of a value. It is often used when a developer wants to indicate that a variable or object property has no value. null in JavaScript is an assignment value. You can assign it to a variable.

For example

Below is an example of null in javascript ?

var demo = null;
alert(demo); //shows null
alert(typeof demo); //shows object

Output

null
object

Difference Table

The following are the key differences between null and undefined ?

Conclusion

In JavaScript, use null to explicitly indicate that a variable has no value or is intentionally empty. Use undefined when something is naturally missing, such as an uninitialized variable or a non-existing object property. null represents intentional absence, while undefined signals an expected missing value.