Explain the difference between null and undefined in JavaScript

In JavaScript, both null and undefined are used to represent the absence of a value, but they have slightly different meanings and behaviors.

null

The value null is a primitive data type that represents the intentional absence of any object value. It is often assigned explicitly to a variable or property to indicate that it has no value or that it is intentionally empty. It is a value that is assigned by the programmer.

Example:

let variable = null;
console.log(variable); // Output: null

undefined

The value undefined is a primitive data type that is automatically assigned to a variable or property when it has been declared but has not been assigned any value. It is the default value given to variables that have not been initialized.

Example:

let variable;
console.log(variable); // Output: undefined

Here are some key differences between null and undefined in JavaScript:

• null is an assignment value that represents the intentional absence of an object value, whereas undefined represents the absence of any assigned value.
• null is a value that can be assigned to a variable explicitly, whereas undefined is a default value assigned automatically by JavaScript.
• null is of type "object", while undefined is of type "undefined".
• When comparing null and undefined using strict equality (===), they are not considered equal because they are of different types.

It's important to note that null and undefined are both "falsy" values in JavaScript, meaning they evaluate to false in Boolean contexts. However, they are not the same and are used in different contexts based on their intended meanings.