Vandana Kumari

Data Types In JavaScript

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Vandana Kumari
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Data Types In JavaScript

What are data types in JavaScript

Data types in JavaScript are used to specify the type of value or data a variable can store or hold and determine the operations that can be performed on it.

How to know the data type of variable?

In Javascript, we can know the data type of a variable using the ‘typeof’ operator.
The ‘typeof’ operator in Javascript is used to check the data type of variable

var name='Code';

var age=13;

console.log(typeof(name)); // string

console.log(typeof(age)); // number

What are different Data Types in JavaScript?

What are data types in JavaScript? - Use My Notes

Primitive Data Type

  • In JavaScript. It can hold only a single value at a time.
  • It includes String, Number, Boolean, Undefined, and Null.
  • These data types are immutable i.e. they can’t be changed or altered.

var a="Hello";

console.log(a[2]); // l

a[2]='L'

console.log([a]); // Hello

Types of primitive data types

String

A string is a data type that is used to store or hold sequence characters enclosed in either single or double quotes. It is used to store data in the form of text.

let name='Vandana';

let msg="Hello";

console.log(msg,name); // Hello Vandana

console.log(typeof(name)); // string

Number

It represents any one integer, floating-point or exponential value.

let a = 123

let b = 1.23

console.log(a); // 123

console.log(b); // 1.23

Boolean

It returns either true or false.

var x=false;

console.log(typeof x);

Undefined

A variable that is declared but not initialized with any value.

var a;

console.log(typeof(a)); // undefined

Null

It represents a null value which means no value. A variable is initialized with null.

var b=null;

console.log(b); // null

console.log(typeof b); // object

Non-primitive/Reference Data Types

  • These are the data types derived from primitive data types. It is used to store or hold multiple values at a time.

  • It includes arrays, objects, and functions.

  • These data types are mutable, i.e. they can be altered or changed.

    let arr=[1,2,3];

    console.log(arr); // [1,2,3]

    arr.push(5);

    console.log(arr); // [1,2,3,5]

    console.log(typeof arr); // object

Types of Non-primitive data types

Object

Elements are stored as a key-value pair.

let obj={ name:'Vandana', age:21};

console.log(obj); // { name:'Vandana', age:21}

console.log(typeof obj); // object

// access value of object

console,log(obj["name"]); // Vandana

console,log(obj.name); // Vandana

Array

It is used to store multiple elements.

let arr=[1,2,true,'Sam'];

console.log(arr); // [1,2, true,'Sam']

// access value from array

console.log(arr[0]); // 1

Function

A function is a block of code enclosed in curly braces used to perform a specific task.

function fun()

{}

console.log(typeof fun); // function

JavaScript