Array Methods in JS

arrayMethods.js

//*********** Array.prototype.map()**********************//
//executes a callback function on each element of the given array and RETURNS A NEW ARRAY
//.map() DOES create a new array. 

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

// pass a function to map
const map1 = array1.map(x => x * 2);

console.log(map1);
// expected output: Array [2, 8, 18, 32]

//***********************************************************//


//*********** Array.prototype.forEach()**********************//

//.forEach() DOES NOT create a new array, it returns the same one
// executes a callback function on each element of the given array
const array1 = ['a', 'b', 'c'];

array1.forEach(element => console.log(element));

// expected output: "a"
// expected output: "b"
// expected output: "c"

//***********************************************************//

//*********** Array.prototype.filter()**********************//
// DOES CREATE A NEW ARRAY
// Applies a condition to the given array and returns A NEW ARRAY with items satisfying the given condition
const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6);

console.log(result);
// expected output: Array ["exuberant", "destruction", "present"]

//***********************************************************//

//*********** Array.prototype.reduce()**********************//

//The reduce() method executes a reducer function (that you provide) 
//on each element of the array, resulting in a single output value.

const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;
//currentValue defaults to 0.
// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer));
// expected output: 10

// 5 + 1 + 2 + 3 + 4
console.log(array1.reduce(reducer, 5));
// expected output: 15

//***********************************************************//


//*********** Array.prototype.find()**********************//
//The find() method returns the value of the first element in 
//the provided array that satisfies the provided testing function.

const array1 = [5, 12, 8, 130, 44];

const found = array1.find(element => element > 10);

console.log(found);
// expected output: 12

//***********************************************************//

//*********** Array.prototype.includes()**********************//

//The includes() method determines whether an array includes a 
//certain value among its entries, returning true or false as appropriate.

const array1 = [1, 2, 3];

console.log(array1.includes(2));
// expected output: true

const pets = ['cat', 'dog', 'bat'];

console.log(pets.includes('cat'));
// expected output: true

console.log(pets.includes('at'));
// expected output: false


//***********************************************************//