What Is An Javascript Array?

Javascript array is an object which stores multiple items of different data types in a single variable. An array’s length always starts with index 0 and ends with total length minus 1. As an array stores multiple items soo we access items by index number.

Table Of Content:

Array Structure:

Let’s say we own various mobile phones from different companies, such as iPhone, Samsung, Redmi, Oppo, Infinix, and Vivo. Without an array, we can store them one by one in this way

let mobile1 = "iphone";
let mobile2 = "Samsung";
let mobile3 = "Redmi";
let mobile4 = "Oppo";
let mobile5 = "Infinix";
let mobile6 = "Vivo";

Example:

  • But in an array, we can store them in a single variable name mobile in the following way. Always declare an array with const.
const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
console.log(mobiles)
  • Line and space in an array do not matter so for better understanding we can write an array like this
const mobiles=
["iphone",
"Samsung",
"Redmi",
"Oppo",
"Infinix",
"Vivo"]
console.log(mobiles)
  • Another way to store in an array is first to make an empty array and then store values 
const mobiles=[];
mobiles[0] = "iphone";
mobiles[1] = "Samsung";
mobiles[2] = "Redmi";
mobiles[3] = "Oppo";
mobiles[4] = "Infinix";
mobiles[5] = "Vivo";

console.log(mobiles)

OUTPUT:

iphone,Samsung,Redmi,Oppo,Infinix,Vivo

Javascript Array Length:

Javascript array length starts with 0 index number and ends with total length minus 1. You can also access the array item with the index number. 0 index is the first item and 1 is the second item.

Here is an example of the index number

const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
mobile= mobiles[0]
console.log(mobile)
 mobile= mobiles[1]
console.log(mobile)
mobile= mobiles[4]
console.log(mobile)
mobile= mobiles[5]
console.log(mobile

OUTPUT:

iphone
Samsung
Infinix
Vivo

Javascript Array
let mobile= mobiles[mobiles.length-1]
console.log(mobile)

OUTPUT:

Vivo

Javascript Array to String:

Javascript  array can be converted into a string by using toString() method

Here is an example:

const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
console.log(mobiles.toString())

Different between Array and Object:

An array is also an object but an Array use number to access its elements while an object use name to access its elements.

Example of array:

const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
console.log(mobiles[1])

Example of Object:

const Class = {firstName:"Rashid", lastName:"Iqbal", age:25};
console.log(Class.firstName);

Adding New Array Elements:

We use the push() method to add a new element to an array. It also increases the length of the existing array. New elements are added to the end of an array, here is an example of adding a new element

const persons=["Ahmad","Rashid","Muna"]
persons.push("Waqas");
console.log(persons)

OUTPUT:

Ahmad,Rashid,Muna,Waqas

Suppose that our array length is 4 and we want to add a new array element at index 7 so index no.5 and 6 remain undefined. It creates a hole in an array.

Here is an example:

const persons=["Ahmad","Rashid","Muna","Waqas"]
persons[7] ="Irfan";
console.log(persons)

OUTPUT:

Ahmad,Rashid,Muna,Waqas,undefined,undefined,Irfan

Javascript Array Instanceof:

The instanceof operator returns true and false values, if the array then true otherwise it returns false.

const persons=["Ahmad","Rashid","Muna","Waqas"]
persons intanceof Array;

Javascript Array sort:

Array sort is used to arrange the elements alphabetically. For this purpose, we use 2 methods one is sort() and the other is reverse()

Here is an example of sort()

const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
mobiles.sort()

OUTPUT:

iphone,Infinix,Oppo,Redmi,Samsung,Vivo

Here is an example of reverse()

const mobiles=["iphone","Samsung","Redmi","Oppo","Infinix","Vivo"]
mobiles.sort()
mobiles.reverse()

OUTPUT:

Vivo,Samung,Redmi,Oppo,Infinix,iphone

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Javascript Array map:

Javascript map() performs a function and returns a new array. It takes three arguments which are

  •     Item value
  •     Item index
  •     Array itself

Here is an example:

const persons=["Ahmad","Rashid","Muna","Waqas"]
persons.map(myfunction)
function myFunction(value, index, array) {
  return value;
}

While the callback function uses only value and returns the same value as an array

Here is an example:

const persons=["Ahmad","Rashid","Muna","Waqas"]
persons.map(myfunction)
function myFunction(value) {
  return value;
}

OUTPUT:

Ahmad,Rashid,Muna,Waqas

How do I know if a variable is an array?

Use typeof operator in javascript to know the array and it always returns an object because the javascript array is an object. Now a day we use the Array.isArray() to solve the problem of an object and it returns an array.

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