Arrays in JavaScript

Important points to note about arrays are given below

1. Arrays are of reference types. (Non Primitives)
2. Arrays can store numbers, strings, objects etc
3. Multi dimensional arrays are supported in JavaScript
4. Each array object supports the methods as defined in Array.prototype
5. Arrays are passed by reference

Array definition Examples

//Array methods
let a = [2,3,'India']
console.log(a.toString()) // output - 2,3,India

//check if element exists
console.log(a.includes(2)) // output - true

//add element from the end
a.push(4)
console.log(a.toString()) // output - 2,3,India,4 

a.push([4,5,6])
console.log(a.toString()) // output - 2,3,India,4,4,5,6

//remove element from the end
console.log(a.pop()) // output - [4,5,6]

console.log(a.toString()) // output - 2,3,India,4

a.shift();
console.log(a.toString()) // output - 3,India,4

a.unshift('65');
console.log(a.toString()) // output - 65,3,India,4

console.log(typeof a[1]) //number

a.splice(2,1)
console.log(a.toString()) // output - 65,3,4


let k = a.slice(0,1)
console.log(a.toString()) // output - 65,3,4

console.log(k.toString()) // output - 65

var emp = [
    { id: 20, name: 'USA' },
    { id: 24, name: 'UK' },
    { id: 56, name: 'Australia' },
    { id: 20, name: 'India' },
    { id: 88, name: 'Canada' }
];

console.log(emp.filter(e => e.id == 20) ) 
//output - [ { id: 20, name: 'USA' }, { id: 20, name: 'India' } ]

console.log(emp.map(e => e.name + 'new') ) 
//output - [ 'USAnew', 'UKnew', 'Australianew', 'Indianew', 'Canadanew' ]

console.log(emp.reduce((p,e) => p + e.id,0) ) //output - 208

console.log(emp.sort((a,b)=>a.id-b.id))
//output 
/*
[ { id: 20, name: 'USA' },
  { id: 20, name: 'India' },
  { id: 24, name: 'UK' },
  { id: 56, name: 'Australia' },
  { id: 88, name: 'Canada' } ]
  */

console.log(emp.sort((a,b)=>b.id-a.id))
//output
/*
[ { id: 88, name: 'Canada' },
  { id: 56, name: 'Australia' },
  { id: 24, name: 'UK' },
  { id: 20, name: 'USA' },
  { id: 20, name: 'India' } ]
  */

console.log(Math.max.apply(null, emp.map(a=>a.id))) //output - 88

console.log(Math.min.apply(null, emp.map(a=>a.id))) // output - 20

//every, foreach, some, find, findIndex
a.forEach((v,i,a)=>
{console.log('inside for' + v);
    })

// output 
/*
inside for65
inside for3
inside for4
*/