JavaScript Data Types - JavaScript Tutorial

There are different types of data that we can use in a JavaScript program. For example,

const x = 9;
const y = "Hello";

Here,

9 is an integer data type.

"Hello" is a string data type.

What are the data types in JavaScript?

In this tutorial, I will explain with examples 8 data types in JavaScript.

• Number type.
• String type.
• Boolean type.
• Null type.
• Undefined type.
• BigInt type.
• Symbol type.
• Object type.

Here, all data types except Object are primitive data types, whereas Object is non-primitive.

Note: The Object data type (non-primitive type) can store collections of data, whereas primitive data type can only store a single data.

A value in JavaScript is always of a certain type. For example, a string or a number.

JavaScript Types are Dynamic

JavaScript has dynamic types. This means that the same variable can be used to hold different data types:

Example:

let n;  // Now n is undefined
n = 9;           // Now n is a Number
n = "Sagar";      // Now n is a String

1. Number

// Number Data Type
let n1 = 34.00;     //  number with decimals
let n2 = 34;        // number without decimals

2. String

let str = "Hello";  // string with double quotes
let str2 = 'Single quotes are ok to use also'; // string with single quotes
let phrase = `can embed another ${str}`; // string with backticks

In JavaScript, there are 3 types of quotes.

• Double quotes: "Hello".
• Single quotes: 'Hello'.
• Backticks: `Hello`.

Example

let name = "Sagar";

// embed a variable
alert( `Hello, ${name}!` ); // Hello, Sagar!

// embed an expression
alert( `the result is ${1 + 2}` ); // the result is 3

/* testing the expression inside double quotes using ${…}
    is not evaluated here.
*/    
alert( "the result is ${1 + 2}" ); // the result is ${1 + 2} (double quotes do nothing)

3. BigInt

// the "n" at the end means it's a BigInt
const bigInt = 1234567890123456789012345678901234567890n;

4. Boolean (logical type)

The boolean type has only two values: true and false.

let x = 2;
let y = 2;
let z = 6;
(x == y)       // Returns true
(x == z)       // Returns false


// Boolean values also come as a result of comparisons:

let isGreater = 4 > 1;
console.log( isGreater ); 
// true (the comparison result is: "yes")