JavaScript Data Types

Data Types in JavaScript

Data types to define what types of data can store values and changed it.

There are following types of data types and strucutre

• Primitive data types
  • boolean
  • number
  • string
  • bigint
  • symbol
• composite data types
  • Object
  • Array
  • Function
• special data types
  • undefined
  • null

Data Types Example in JS

Some examples are primary data types in JavaScript

var age = 18;			// Number
var name = "Amit Kumar";	// String
var obj = {name:"Raj Kumar"};	// Object

Dynamic Data Types in JavaScript

JavaScript is a loosely typed and dynamic language. JavaScript variables not correlated data value so It can change

var a;					//a is undefined
var a = 18;				//a is Number
var a = "Amit Kumar";	//a is String

Example

/*
In this example 16 is treated as string like "Apple" + "16"
*/
var a = "Apple" + 16;
// Output : Apple16

var a ="3" + 16;
// Output : 316

Example

var a = "16" -3;
// Output : 13

var a = "16" - "3";
// Output : 13

JavaScript typeof Operator

typeof operator used to check the type of variable. This can be used with or without parentheses like (typeof(a)) or (typeof a).

Example

//Strings
typeof '';		// Returns "string"
typeof "";		// Returns "string"
typeof 'ABCD';		// Returns "string"
typeof '456';		// Returns "string"
typeof "456";		// Returns "string"

//Numbers
typeof 0		// Returns "number"
typeof 456		// Returns "number"
typeof 45.3		// Returns "number"
typeof (45+6)		// Returns "number"
typeof (456)		// Returns "number"
typeof 3.5e-2		// Returns "number"
typeof Infinity		// Returns "number"
typeof NaN		// Returns "number"

// Booleans
typeof true;		// Returns "boolean"
typeof false;		// Returns "boolean"

// Undefined
typeof undefined;		// Returns "undefined"
typeof undeclared_variable;	// Returns "undefined"

// Null
typeof null;		// Returns "object"

// Objects
typeof {};		// Returns "object"
typeof {name: "ABC"};	// Returns "object"

// Arrays
typeof [];  		// Returns "object"
typeof [4,5,6]; 	 // Returns "object"

// Functions
console.log(typeof isNaN);	// Returns "function"
typeof function(){};		// Returns "function"

JavaScript Strings Data Types

A String is set of characters like "Vipin Kumar", it is denoted by single quotes '' or "" double quotes

Example

var name1 = 'Vipin Kumar';	// using single quotes
var name2 = "Vipin Katiyar"; 	// using double quotes

We can use single quotes inside the string

Example

var m = "It's fine"; // single quote inside double quotes
var n = 'It\'s fine'; // escaping single quote with backslash
var p = 'I am fine and "You"';  // double quotes inside single quotes
var q = "I am fine and 'You'";     // single quotes inside double quotes

JavaScript Numbers Data Type

A Numbers data type is number with or without decimals, positive or negative, or numbers written using exponential notation e.g. 1.8e-4 (0.00018)

Example

typeof 0		// Returns "number"
typeof -456		// Returns "number"
typeof 456		// Returns "number"
typeof 45.3		// Returns "number"
typeof (45+6)		// Returns "number"
typeof (456)		// Returns "number"
typeof 3.5e-2;		// Returns "number"
typeof Infinity;	// Returns "number"
typeof NaN;		// Returns "number"

Example : Infinity

console.log(456 / 0);	//Infinity
console.log(-456 / 0);	//-Infinity
console.log(456 / -0);	//-Infinity
console.log(-456 / -0);	//Infinity

Example : NaN

console.log('test' / 3); // NaN
console.log('test' / 3+4); //NaN

JavaScript Boolean Data Type