Array


let fruits = ['apple', 'banana', 'kiwi', 'grape'];
let nums = [4, 6, 204, 52, 5];

Accessing array elements:


let seasons = ['Winter', 'Spring', 'Summer', 'Autumn'];

seasons[2];  // 'Summer'
seasons[0];  // 'Winter'

List of methods and techniques which are used to modify an array itself:

Add new elements:

push

The push() method is used to add one or more elements at the end of array.

let numbers = [4, 22, 13];
numbers.push(8);  // [4, 22, 13, 8]

unshift

The unshift() method is used to add new elements to the start of the array.

let phones = [
    { name: 'Samsung',  color: 'white', number: 5 },
    { name: 'Apple',  color: 'black', number: 7 },
    { name: 'Xiaomi',  color: 'gold', number: 4 },
]

phones.unshift({ name: 'Huawei',  color: 'blue', number: 6 });  

/*
  [
      { name: 'Huawei',  color: 'blue', number: 6 },
      { name: 'Samsung',  color: 'white', number: 5 },
      { name: 'Apple',  color: 'black', number: 7 },
      { name: 'Xiaomi',  color: 'gold', number: 4 },
  ]
*/

splice

The splice() method is used to insert (and/or) remove elements in the array.

let animals = ['tiger', 'monkey', 'giraffe', 'fox', 'panda', 'lion'];
animals.splice(2, 0, 'elephant');
console.log(animals);  // expected output: ['tiger', 'monkey', 'elephant', 'giraffe', 'fox', 'panda', 'lion']

Remove elements:

pop

The pop() method removes the last element of the array and returns it.

let cars = ['Honda', 'Toyota', 'Nissan', 'Mercedes', 'Chevrolet', 'BMW'];
let removed = cars.pop();
console.log(cars);  // expected output: ['Honda', Toyota, 'Nissan', 'Mercedes', 'Chevrolet']
console.log(removed);  // expected output: 'BMW'

shift

The shift method is used to remove first element from the array.

let colors = ['red', 'orange', 'yellow', 'pink', 'black', 'brown', 'grey'];
let removed = colors.shift();
console.log(colors);  // expected output: ['orange', 'yellow', 'pink', 'black', 'brown', 'grey']
console.log(removed);  // expected output: 'red'

splice

The splice() method is used to insert (and/or) remove elements in the array.

let animals = ['tiger', 'monkey', 'giraffe', 'fox', 'panda', 'lion'];
let removed = animals.splice(2, 3, 'elephant', 'turtle');
console.log(animals);  // expected output: ['tiger', 'monkey', 'elephant', 'turtle', 'lion'];
console.log(removed);  //expected output: ['giraffe', 'fox', 'panda']

delete operator

let fruits = ['apple', 'kiwi', 'banana', 'peach'];
delete fruits[1];
console.log(fruits);  // expected output: ['apple', undefined, 'banana', 'peach']

length

let nums = [5, 2, 72, 19, 15, 0, 23];
nums.length = 3;
console.log(nums);  //expected output: [5, 2, 72]

Get the array length:

let cars = ['Honda', 'Toyota', 'Nissan', 'Mercedes', 'Chevrolet', 'BMW'];
cars.length;  // 6

Copy an array use slice() method or spread syntax:

let actors = ['Al Pacino', 'Johnny Depp', 'Tom Hanks', 'Leonardo DiCaprio'];
let actorsCopy = actors.slice();
let actorsCopy2 = [...actors];

Merge two or more arrays use concat() method:

let portion1 = [1, 2, 3, 4];
let portion2 = [5, 6, 7];
let nums = portion1.concat(portion2);
console.log(nums);  // expected output: [1, 2, 3, 4, 5, 6, 7]

Common methods

MDN: Array