A data type describes a set of values and the operations possible on those values.

Table of Contents

Primitive

The predefined data types provided by JavaScript language are known as primitive data types. Primitive data types are also known as in-built data types.

Number

In programming, generally, numbers are categorized into two groups — integers and floats.

An integer is a whole number without a decimal point.

Ex:

let num = 2; // Integer

1	let num = 2; // Integer

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A float, or floating-point number, is a number with a decimal point.

Ex:

let num2 = 1.3; // Floating point number

1	let num2 = 1.3; // Floating point number

However, JavaScript doesn’t make any distinction between integers or floats whatsoever — we’ve got only one type for numbers in the language and that is the type ‘number‘.
Ex:

Console:
>> 4 + 6
10
>> 4.6 + 3
7.6
>> 2 - 5
-3
>> 2.5 - 1
1.5

Console:

>> 4 + 6

>> 4.6 + 3

7.6

>> 2 - 5

-3

>> 2.5 - 1

1.5

All the numbers shown above are known as number literals.

A literal is an exact representation for a value in the code.

Note:
Besides regular numbers, there are so-called “special numeric values” which also belong to this data type: Infinity, -Infinity and NaN.
Infinity represents the mathematical Infinity ∞.
NaN represents a computational error.

Strings

A string is a sequence of textual characters.

A string can be denoted using a pair of single quotes (''), or a pair of double quotes (""), or a pair of backticks ()
Ex:

var lang = 'JavaScript';
var os = "Windows";
var phrase = `can embed ${str}`;

var lang = 'JavaScript';

var os = "Windows";

var phrase = `can embed ${str}`;

Double and single quotes are “simple” quotes.
Backticks are “extended functionality” quotes. They allow us to embed variables and expressions into a string by wrapping them in ${…}.

Booleans

A Boolean is simply a true or false value.

In JavaScript, a Boolean is denoted using the literal values true and false.

Ex:

var proceed = true;
var stopNow = false;

1 2	var proceed = true; var stopNow = false;

NULL

NULL represents “nothing”, “empty” or “value unknown”.

Ex:

let age = null;

1	let age = null;

Underfined

The meaning of undefined is “value is not assigned”.

Ex:

let x;
console.log(x);  // undefined

1 2	let x; console.log(x); // undefined

Symbol

Symbol for unique identifiers.

Symbols return unique identifiers that can be used to add unique property keys to an object that won’t collide with keys of any other code that might add to the object. They are used as object properties that cannot be recreated. It basically helps us to enable encapsulation or information hiding.

let symbol1 = Symbol("Geeks")
let symbol2 = Symbol("Geeks")
  
// Each time Symbol() method 
// is used to create new global Symbol
console.log(symbol1 == symbol2); // False

let symbol1 = Symbol("Geeks")

let symbol2 = Symbol("Geeks")

// Each time Symbol() method

// is used to create new global Symbol

console.log(symbol1 == symbol2); // False

BigInt

BigInt type was recently added to the language to represent integers of arbitrary length.

A BigInt value is created by appending n to the end of an integer:

// the "n" at the end means it's a BigInt
const bigInt = 1234567890123456789012345678901234567890n;

1 2	// the "n" at the end means it's a BigInt const bigInt = 1234567890123456789012345678901234567890n;

Object data types

Arrays

An array is an ordered collection of data.

An array is like a sequence of values or a list of items. It has the capability of storing multiple values under one hood. The individual values of an array are formally called elements, or items, of the array.

Each element sits at a given position, formally known as its index in the array. The total number of element is referred to as the array’s length.

Note:
Strings and arrays are both sequences of data. Hence the same concepts of indexes and length apply to both of them.

Ex:

var nums = [1, 5, 10];

1	var nums = [1, 5, 10];

Functions

A function defines a piece of code that gets executed when the function is called.

A function is used to group together some code that could be executed later on at will. This execution is initiated by calling — or better to say, invoking — the function.

The function keyword is used to create a function in JavaScript.

Syntax:

function functionName( parameterList ) {
statements
}

Ex:

function sayHello() {
   var name = prompt('Enter your name:');
   document.write('Hello, ' + name + '.');
}

sayHello(); // call the function

function sayHello() {

var name = prompt('Enter your name:');

document.write('Hello, ' + name + '.');

}

sayHello(); // call the function

Objects

An object is a set of properties and methods.

There are many different kinds of objects in JavaScript. Arrays, as we saw above, are objects. Functions are objects too.

In this section, we are concerned with the actual object data type in JavaScript that denotes the purest of all objects.

Here’s the syntax of an object literal:

{key1: value1, key2: value2, …, keyN: valueN}
or
{
key1: value1,
key2: value2,
…,
keyN: valueN
}

Ex:

var obj = {x: 10, y: 20};

1	var obj = {x: 10, y: 20};

var url = {
   protocol: 'https',
   domain: 'www.codeguage.com',
   path: '/'
};

var url = {

protocol: 'https',

domain: 'www.codeguage.com',

path: '/'

};

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