Null and Undefined

In JavaScript, there are seven primitives: String, Number, Boolean, Null, Undefined, Symbol and BigInt. And now it focuses on Null and Undefined.

Undefined

• Indicates the absence of a value.
• A variable declared but not assigned anything is called undefined.

let a
console.log(a) // undefined

• A function that returns nothing result in undefined.

const returnsNothing = () => {}
const test = returnNothing()

console.log(test) // undefined

Null

• Represents “nothingness”
• Developers explicitly set a value to null.

const person = {
  firstName: "Reza",
  middleName: "Fauzi",
  lastName: "Augusdi",
  nickName: null
}

console.log(persone.nickName) // null

Difference

• null and undefined are different.
• null === undefined results in false.

Summary

Undefined means no value assigned, while Null represents intentional nothingness. They are distinct primitives in JavaScript.