Difference Between null and undefined

In JavaScript, null and undefined are primitive data types used to indicate the absence of a value, but they have different meanings and use cases.

• undefined — means something is not defined. For example, a variable is created but nothing is assigned to it:

let x; // x is undefined because we didn't assign a value
console.log(x); // undefined

• null — means you explicitly stated that there's nothing here. For example:

let y = null; // y is "nothing" because we decided so
console.log(y); // null