Array object and Frequently used Array Methods in Java Script ES6

Array in Java Script

• Arrays are list-like objects which user can store data and manipulate,
• Array objects in Java Script has built in methods to perform operations,
• An array is a special variable, which can hold many values
• Arrays highly used data structure in any language as well as JavaScript

Creating array normal way in java script (es6)

const array_name = [item1, item2, ...];

Creating Array using new keyword

const array_name = new Array(item1, item2,item3,.......);

Accessing array item using index

let cars = ['BMW', 'Volvo']

console.log(cars.length)

Add an item to the end of an Array

let cars = ['BMW', 'Volvo']

cars.push('Tesla')

// ['BMW', 'Volvo', 'Tesla']

Remove an item from an Array

let cars = ['BMW', 'Volvo']

cars.push('Tesla')

let last = cars.pop() // remove Tesla (from the end)
// ['BMW', 'Volvo']

Find index of element in array

let pos = cars.indexOf('Volvo')
// 1

Array.prototype.concat()

• The concat() method is used to merge arrays. This method does not change the existing arrays, but instead returns a new array.

const array1= [1,2,3];
const array2 = [4,5,6];
const array3 = array1.concat(array2);

console.log(array3);
// expected output: Array [1,2,3,4,5,6]

Array.prototype.filter()

• The filter() method creates a new array which satisfies the given condition

const words = ['neogcamp', 'HTML', 'Tanay Pratap', 'ReactJs',  'CSS'];

const result = words.filter(word => word.length > 5);

console.log(result);
// expected output: Array ["neogcamp", "Tanay Pratap", "ReactJs"]

Array.prototype.map()

• The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

const array1 = [1, 4, 9, 16];

// pass a function to map
const map1 = array1.map(x => x * 5);

console.log(map1);
// expected output: Array [5, 20, 45, 80]