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JavaScript Data Types

Variables in JavaScript

Before moving to JavaScript Data types first we will read about JavaScript variables. Variables are the container for storing data values. It is a name of the storage location where the data is actually stored.

Declaration of JavaScript Variable

There are 2 ways by which we can declare the JavaScript variables

  • By using var
  • By using let


var a = 2;
var b = 6;
var c= a*b;
console.log("a is: " + a);
console.log("b is: " + b);
console.log("c is: " + c);

let a = 2;
let b = 6;
let c= a*b;
console.log("a is: " + a);
console.log("b is: " + b);
console.log("c is: " + c);

Rules for the naming of JavaScript Variable

  • Variable names must begin with a letter. It can also begin with _ and $ symbol.
  • The first character of variable name must not be a digit.
  • Variable names can contain letters, digits, underscores, and dollar signs.
  • Variable names are case sensitive (A and a are different variables, not same )
  • JavaScript keyword cannot be used as variable names for example let, class, return  are reserved in JavaScript. 

Data Types in JavaScript

There are two types of data types in JavaScript

  • Primitive data type

Primitive data type includes String ,Numbers ,Boolean , null, Undefined , Symbol.

  • Non-primitive data type

Non-primitive data type includes Arrays, Object literals, Dates.

Data TypesExplanationExample
StringString is used to store text . It is a sequence of characters.
String content is wrapped inside ' ' or " ".
let a= ‘JavaScript’ ,
let b= “JavaScript”
NumbersNumber represents numeric value like Integer and Float.let a = 10,
let b = 10.5
BooleanBoolean represents two values true or false .let a =true ,
let b = false
nullnull represents empty value.
It means the variable a is empty.
let a= null;
UndefinedVariable without any value is undefined.let a;
ArraysArray store multiple value of the same data type.
Arrays are written with square brackets and array items are separated by commas.
let a = [“abc'”, “xyz”]
Object literalsObject properties are written as key : value pairs and separated by commas and end with semicolon.
It is a complex data type.
let a = {
name: “xyz”,
marks: 12
DateDate object represents date & time. It includes days, months, years, hours, minutes, and seconds.let date = new Date(“28 July 2022”);
JavaScript Data Types

JavaScript typeof

To find the data type of a variable we use of typeof Operato in JavaScript.

For Example

let name = 'Mohan';
typeof(name); // returns "string"

let val = true;
typeof(val); //returns "boolean"

let marks = 44;
typeof(marks); //returns "number"

const  x = null;
typeof(x); // returns "object"

Before JavaScript Data types tutorial read about JavaScript introduction . JavaScript is a dynamic type language. It automatically determines the variables data type. This is all about JavaScript data types and variables.

Written By : Ankita Kataria.
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