JS Data Types

Ø  A data type specifies the amount of memory that allocates to a value associated with it. A data type also determines the operations that you can perform on it.

Ø  Data types in JavaScript describe the different types or kinds of data that you will be working with and storing in variables.

Ø  JavaScript is a dynamic and loosely typed language. It means you don't require to specify a type of variable.

Ø  A variable in JavaScript can be assigned any type of value, as shown in the following example.

var myvariable = 0; // numeric value


myvariable = 'ten'// string value


myvariable = 10.0// decimal value


myvariable = true// Boolean value


myvariable = null// null value


In general, there are eight basic data types in JavaScript. Seven of them are primitive types: number, string, Boolean, null, undefined, symbol, and BigInt, and the other one is a complex type: object.

Ø  String: represents textual data.

Example “Hello World!” ‘Hello’

Ø  Number: an integer or a floating-point number.

Example: 3, 3.234, 3e-2, etc.

Ø  BigInt: an integer with arbitrary precision.

Example: 900719925124740999n, 1n, etc.

Ø  Boolean: Any of two values: true or false.

Example: true and false

Ø  Undefined: a data type whose variable is not initialized.

Example: let a;

Ø  Null: denotes a null value.

Example: let a = null;

Ø  Symbol: data type whose instances are unique and immutable.

Example: let value = Symbol('hello');

Ø  Object: key-value pairs of collection of data.

Example let student = { };

1)   String

Ø  The string is used to store text.

Ø  In JavaScript, strings are surrounded by quotes.

Ø  This type of data is extremely common in JavaScript.

Ø  Strings are written in single or double quotes.

Ø  Single quotes and double quotes are practically the same and you can use either of them. For example:

 console.log(""); // empty string

 console.log("Hello"); // one word

 console.log("Hello, world"); // a phrase

 console.log('a');  // single character

 console.log('1234'); // a sequence of digits


Ø  Note: any digits in quotes will also be considered a string.

2)   Number

Ø  The number represents integer and floating numbers (decimals and exponentials). Numbers are the most important thing for any programmer.

Ø  You can use positive, negative numbers, and zeros. There are no additional difficulties in recording floating-point numbers.

Ø  Integer numbers can be used to count physical objects, while floating-point numbers are a good choice for statistical and scientific calculations. For example:






3)   BigInt type

Ø  The BigInt type represents the whole numbers that are larger than 253 – 1. However, if you need to use a larger number than that, you can use the BigInt data type.

Ø   A BigInt number is created by appending n to the end of an integer. For example,

let value1 = 900719925124740998n;


4)   Boolean

Ø  This data type represents logical entities. Boolean represents one of two values: true or false. For example:

let a = true;

let b = false;

console.log(typeof b); // Boolean



Ø  In general, JavaScript allows values of other types to be converted into Boolean values of true or false.

Ø  To convert a value of another data type into a Boolean value, you use the Boolean () function.

5)   undefined

Ø  The undefined data type represents the value that is not assigned.

Ø  If a variable is declared but the value is not assigned, then the value of that variable will be undefined. For example:

let name;

console.log(name); // shows "undefined"



6)    null

Ø  In JavaScript, null is a special value that represents an empty or unknown value. For example:

let name= null;

console.log(name); // shows "null"



Ø  Notenull is not a “reference to a non-existing object” or a “null pointer” like in some other languages.

7)   Symbol

Ø  A Symbol is a unique and immutable primitive value.

Ø  This data type was introduced in a newer version of JavaScript.

Ø  The purpose of symbols is to create unique property keys that are guaranteed not to clash with keys from other codes.

Ø  You use the Symbol () function to create a Symbol.

Ø  A value having the data type Symbol can be referred to as a symbol value.

Ø   The symbol is an immutable primitive value that is unique. For example:

let name1 = Symbol('John');

let name2 = Symbol('John');


Ø  name1 and name2 both contain John, they are different as they are of the symbol type.

8)   Objects

Ø  An object is a complex data type that allows us to store collections of data.

Ø  An object holds multiple values in terms of properties and methods.

Ø  In JavaScript, an object is a collection of properties, where each property is defined as a key-value pair. For Example:

var person = {

    Fname: 'John',

    Lname: null,

    age: 20



Ø  If want to access an object’s property, you can use; the dot notation (.) and the array-like notation ([]). For Example:




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