Nicos Garden

Arrays

2 min read

Arrays

const fruits = ['apple', 'orange', 'banana'];
// Different data types
const data = [1, 'chicken', false];

Property .length

const numbers = [1, 2, 3, 4];
numbers.length; // 4

Index

const myArray = [100, 200, 300];
console.log(myArray[0]); // 100
console.log(myArray[1]); // 200

Mutable chart

addremovestartend
push✔✔
pop✔✔
unshift✔✔
shift✔✔

Array.push()

// Adding a single element:
const cart = ['apple', 'orange'];
cart.push('pear');
 
// Adding multiple elements:
const numbers = [1, 2];
numbers.push(3, 4, 5);

Add items to the end and returns the new array length.

Array.pop()

const fruits = ['apple', 'orange', 'banana'];
const fruit = fruits.pop(); // 'banana'
console.log(fruits); // ["apple", "orange"]

Remove an item from the end and returns the removed item.

Array.shift()

let cats = ['Bob', 'Willy', 'Mini'];
cats.shift(); // ['Willy', 'Mini']

Remove an item from the beginning and returns the removed item.

Array.unshift()

let cats = ['Willy', 'Bob']; //['Willy', 'Bob']
cats.unshift('Willy'); // ['Bob']

Add items to the beginning and returns the new array length.

Array.concat()

const numbers = [3, 2, 1];
const newFirstNumber = 4; // => [ 4, 3, 2, 1 ]
[newFirstNumber].concat(numbers); // => [ 3, 2, 1, 4 ]
numbers.concat(newFirstNumber);

If you want to avoid mutating your original array, you can use concat.

Array.reduce()

const numbers = [1, 2, 3, 4];
 
const sum = numbers.reduce((accumulator, curVal) => {
  return accumulator + curVal;
});
 
console.log(sum); // 10

Array.map()

const members = ['Taylor', 'Donald', 'Don', 'Natasha', 'Bobby'];
 
const announcements = members.map((member) => {
  return member + ' joined the contest.';
});
 
console.log(announcements);

Array.forEach()

const numbers = [28, 77, 45, 99, 27];
 
numbers.forEach((number) => {
  console.log(number);
});

Array.filter()

const randomNumbers = [4, 11, 42, 14, 39];
const filteredArray = randomNumbers.filter((n) => {
  return n > 5;
});

Graph View