Tuesday, March 9, 2021

What are data types in Javascript?

 A) Values in Javascript will have a type.

B) There are 8 basic data types in Javascript.

1) String

let name = 'Test';  

String in Javscript is surrounded by quotes. 

Quotes can single, double quotes.

2) Number

let n = 10;  // Number

3) Boolean

let checkName =  true;

let checkData = false;

4) "null" 

It contains only null value. 

In Javascript, null is not a reference to a non existing object or null pointer. 

It just represents empty or unknown value.

let a= null;

5) "undefined"

It also represent special type, here the variable is declared but not assigned any value as shown below,

let a;

6) bigint

Used to store integers value of arbitrary length.

bigint value is created by appending n to the end of an integer.

const = 11111111112222222223333333333344444444n;

7) object

a) object are used to store collections of data and more complex entities.

b) objects can be created using {...} with optional list of properties, a property is "key": "value" pair.

c) Creating an empty object,

let studentDetail = {};

let steudentDetail = new Object();

d) Creating an object with properties,

let studentDetail = {

"name": "Test",

"rollNo": 1,

"Full Name": "Test User"


e) To access the property values use dot notation or array notation in case of space in key name as shown below,

studentDetail.name  // dot notation

To access full name use array notation as it has space.

studentDetail[Full Name]   // array notation

f) Adding a value to property,

studentDetail.department = 'Computer Science';

g) We may add comma to last property as shown below.

let studentDetail = {

name: "Test",

rollNo: 1,


h) To access the keys use,


i) Use JSON.stringify to convert object to string

var jsonStrng= JSON.stringify(studentDetail);


"{"name":"Test","rollNo":1,"Full Name":"Test User"}"

j) Use JSON.parse to convert string to object

Object = JSON.parse(jsonStrng);

{name: "Test", rollNo: 1, Full Name: "Test User"}

k) The below are also different kinds of object in Javascript,




8) symbol

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