Arrays in

Ahmed Murtaza 😎

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It is a data structure consisting of a collection of elements, Each identified by at least one array index or key

Applications of Array

Array of Donuts

Array of links, icons and thumbnails

Declaration

let arr = new Array(1,2,3);

let arr = Array(1,2,3);

let arr = [1,2,3];

In most languages, the elements of an array required to be of same type. JavaScript allows an array to contain any type of values:

var arr = [  'string', 42.0, true, false, null,      
    undefined,  ['sub', 'array'], 
    {object: true}, NaN
];

Accessing & Assigning in Array

var arr = [27,"Karachi",true];
arr[0]; // 27

var arr = [27,"Karachi",true];
arr[3] = 72;

arr; // [27, "Karachi", true, 72]

Accessing

Assigning

.length

var colors = ['Red', 'Blue', 'Yellow']; 
console.log(colors.length); // 3

var arr = Array(10);  // Creates an array 
//with no element, but with  arr.length set to 10


// The above code is equivalent to
var arr = [];
arr.length = 10;

example

var colors = ['Red', 'Blue', 'Yellow']; 
console.log(colors.length); // 3 

colors.length = 2; 
console.log(colors); // ["Red","Blue"] - Yellow has been removed 

colors.length = 0; 
console.log(colors); // [] the colors array is empty 

colors.length = 3; 
console.log(colors); // [undefined, undefined, undefined]

Iterating Array values

let colors = ['red', 'green', 'blue']; 

for (let i = 0; i < colors.length; i++) {   
   console.log(`Color is ${colors[i]}`); 
}

Array Built-in Methods

concat

pop

push

shift

unshift

.concat()

let myArray = new Array("33", "44", "55");  

myArray = myArray.concat("3", "2", "1"); 

console.log(myArray); // ["33", "44", "55", "3", "2", "1"]

The concat() method joins two arrays and returns a new array:

.pop()

let myArray = new Array("1", "2", "3"); 

let last = myArray.pop(); // "3"

myArray // ["1", "2"]

The pop() method removes the last element from an array and returns that element

.push()

let myArray = new Array("1", "2"); 

myArray.push("3"); // 3

myArray // ["1", "2", "3"]

The push() method adds elements to the end of an array and returns the resulting length of the array

.shift()

let myArray = new Array ("1", "2", "3"); 

let first = myArray.shift(); // "1"

myArray // ["2", "3"]

The shift() method removes the first element from an array and returns that element

.unshift()

let myArray = new Array ("1", "2", "3"); 

myArray.unshift("4", "5"); // 5

myArray // ["4", "5", "1", "2", "3"]

The unshift() add elements to the Front of an array and returns the new length of it

Thank You

ahmedgmurtaza