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What is the difference between null value and undefined value in JavaScript?

What is the difference between null value and undefined value in JavaScript?

Are you looking for the best programming language to develop a web or mobile app? Well, JavaScript is one of the most popular programming languages. It lets the developer implement complex features on the webpage. In addition, you can use JavaScript on the server-side and client-side, making the web page collaborative. It offers interactive elements to the webpage, which engage users where CSS and HTML languages provide the style and structure to the web page.

Null and undefined are types and values in JavaScript, creating errors and keywords in the other programming languages. It is similar to number and character, which means null has 0’s and 1′ configuration. It shows its value and type are null and related to undefined. In addition, use it in the programming language to act as a placeholder for enabling the scriptwriter to know when variables have no value. Continue reading to learn about the JavaScript null and undefined:

READ ALSO: Essential Functions Of JQuery: Web Developers Must Know

Overview of null and undefined 

The value null mentions a non-existent object that means nothing or is empty. Besides, undefined denotes that a variable declares, but didn’t allocate any value. Therefore, use both values to express smoothing absence. Null and undefined are distinct types invalid is an object, and undefined is enter (unclear).

In JavaScript, an undefined variable’s name is assigned from the memory’s space that contains the variable. However, the program writer doesn’t process the memory space yet, showing it as a compile-time error. The variable is null in other programming languages, but the value null identifies the memory space as a reference. The pointer (reference) indicates invalid memory addresses (usually 0x0). Use the pointer used while the developer completes the variable value and needs to clear it with determination by factually representing it to nobody.

Difference between Null and Undefined in JavaScript

Here we provide the difference between the null and undefined values in the programming language. It helps beginners to increase their programming skills. Let’s see null vs undefined:


Null is merely a theoretical concept, which has the function of symbolizing nothingness. JavaScript null represents an intentionally absent object. In TypeScript, null has only one value, and use the null keyword to define the Null type. The reason why it doesn’t help is that the developer can put a null value on it.

  • Null is an assignment value that assigns to variables. It directs that variables don’t point to any object.
  • It is the primitive value that signifies the empty, non-existent and null.
  • Besides, null is an object that points out the missing importance of variables in the program.
  • It is converted to zero (0) while executing a primitive process.


Undefined is one of the properties of a JavaScript global object that develops at run time. The variable has been assigned, but its value has not been set. It will be unclear if no one provides arguments for function restriction. Furthermore, processes do not return a deal, and they return undefined. Both JavaScript and TypeScript contain uninitialized variables. Undefined has only one uninitialized value. There is nothing helpful about TypeScript’s undefined keywords because the programmers can only assign an undefined value to them. 

  • Undefined is not an assignment value which means they declare the variable and do not dispense the value.
  • The undefined value is a type itself.
  • Moreover, it’s a primitive value that replaces a variable that didn’t assign a value.
  • It converts to NaN when executing the primitive task.
  • Moreover, undefined shows the nonexistence of the variable itself.

Features of JavaScript null

The followings are some features of JavaScript null:

     Null is falsy 

Every developer should know many falsy values in a programming language. Let’s see some six falsy deals:

  • false
  • “”(empty string)
  • 0 (zero)
  • NaN (Not A Number)
  • null
  • undefined

Other values in the programming language consider as truthy. JavaScript will coerce null to false in different conditionals. The following are some examples:

const square = null;

if (square) {

  console.log(‘The square is not null’);

} else {

  console.log(‘The square is null’);



The square is null

The square variable is null, so when the statement determines it to be wrong and implements the declaration in the else section.

     typeof null is an object

Using the typeof value, you can find out what type the value is. Here’s an example:

console.log(typeof 10); // ‘number’

Code language: JavaScript (javascript)

Surprisingly, the typeof null returns’ object’:

console.log(typeof null); // ‘object’

null is one of the primitive values and not objects in the programing language. But in the first javascript version, it is historical errors, which might never fix.

Primitive value in JavaScript

In addition, you should know the primitive value in JavaScript that helps you create the app effectively. JavaScript has six primitive values such as

  • Null
  • Undefined
  • Symbol
  • Number
  • Boolean
  • String

Other values in the programming language are objects (array, objects, functions and more).

It is remarkable that it returns object when checking null with typeof:

let a = null;

let b;

console.log(typeof a);

// object

console.log(typeof b);

// undefined

Meanwhile, the JavaScript beginning is generally concerned as an error in the implementation of real JavaScript.

Now, Javascript is used for web browsers and other web-based applications. It lets the developers add interactive behavior to the websites and creates the backend infrastructure with the help of Node.js.


Both undefined and null are not similar. Understanding the difference between null and undefined is essential before writing code to create an application. As a result, the programmer can prevent bugs in the code and know why it occurs. When you understand the null and undefined JavaScript, you will complete the project quickly.

If you have doubts about JavaScript, you can contact JDM Web Technologies. They have certified experts to provide an answer to your queries. The professionals also help you to guide for creating the web applications. 

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