Javascript Difference between null and undefined

In this post, we will learn on differences between null and undefined. This is most common interview question in javascript interview questions

Difference between Null and Undefined:

In JavaScript, null and undefined are two special values that are used to represent the absence of a value. However, there is a difference between them:

• undefined is a value that is assigned to a variable that has been declared but has not been assigned a value. It is also the default value for function arguments that have not been provided. In other words, undefined means a variable has been declared but has no value.
• null, on the other hand, is a value that is explicitly set to represent the absence of any object reference. It represents a deliberate non-value, and can be assigned to a variable to indicate that it is intentionally empty.

Here’s an example to illustrate the difference:

let x;
console.log(x); // undefined

let y = null;
console.log(y); // null

In this example, the variable x is declared but not assigned a value, so its value is undefined. The variable y is explicitly set to null.

So, undefined is a value that indicates the absence of a value, while null is a value that indicates the intentional absence of any object reference.

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