Null vs Undefined in Javascript

Null is an assignment value. It can be assigned to a variable as a representation of no value:

There are two features of null you should understand

1. null is an empty or non-existent value.
2. null must be assigned
3. When you assign null to a variable, you are declaring that this value is explicitly empty.

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

Undefined usually means a variable has been declared, but not defined.

When you try to access a property of an object that doesn't exist you will get undefined in return.

const shashank = {
    name : 'Shashank',  
}

console.log(shashank.age) // undefined

• Both nulland undefinedare primitive values in JavaScript.
• When you do loose equality check on both it returns true

null == undefined // true

because both are considered falsy values.

Summary

• null is an assigned value. It means nothing.
• undefined typically means a variable has been declared but not defined yet.
• null and undefined are falsy values.
• null!== undefined (strict equality) , but null == undefined ( loose equality)