What Is Data Type in JS?


Angela Bailey

What Is Data Type in JS?

JavaScript is a versatile programming language that allows you to work with different types of data. Understanding data types is fundamental to writing effective and efficient code. In this article, we will explore the various data types in JavaScript and learn how they are used.

Primitive Data Types:

JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol. These data types directly represent a single value and are immutable (cannot be changed).


A string is a sequence of characters enclosed in single quotes (”) or double quotes (“”). For example:

let name = "John";
let message = 'Hello, World!';


The number data type represents numeric values. It can be an integer or a floating-point number. For example:

let age = 25;
let pi = 3.14;


Boolean represents logical values – true or false. It is commonly used for conditional statements and comparisons. For example:

let isTrue = true;
let isFalse = false;

null and undefined:

The null data type represents the intentional absence of any object value, while undefined indicates that a variable has been declared but has not been assigned any value yet.

  • null – Represents the absence of any object value.
  • undefined – Indicates that a variable has been declared but has not been assigned any value.


Symbols are unique and immutable values that can be used as property keys in objects. They are often used to define private object properties.

Non-primitive Data Types:

Apart from the primitive data types, JavaScript also has non-primitive or complex data types, also known as reference types. These include object, array, and function.


An object is a collection of key-value pairs and represents real-world entities. It can contain properties and methods.

For example:

let person = {
  name: "John",
  age: 25,
  sayHello: function() {
    console.log("Hello! ");


An array is an ordered list of values enclosed in square brackets ([]). It can store multiple values of any data type. For example:

let numbers = [1, 2, 3, 4, 5];
let fruits = ["apple", "banana", "orange"];


A function is a block of reusable code that performs a specific task. It can be defined using the function keyword and can accept parameters and return values. For example:

function add(a, b) {
  return a + b;

In conclusion, understanding data types in JavaScript is crucial for effective programming. By knowing how to work with different data types, you can manipulate and use data in your code more efficiently. So take your time to familiarize yourself with these data types and practice using them in your JavaScript projects!

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