常用的陣列方法

（此篇會再加上描述）

forEach()

• 單純針對陣列中每個元素一一傳入

var array = ['a', 'b', 'c'];

array.forEach(function(item, index, array){
	console.log(item, index, array)); 
} 

map()

• 會產生新的陣列或新值

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

const map = array.map(x => x * 2);

console.log(map); //  [2, 8, 18, 32]

filter()

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

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

console.log(result);  // ["exuberant", "destruction", "present"]

find()

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

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

console.log(found); // 12

every()

const isBelowThreshold = (currentValue) => currentValue < 40;

const array1 = [1, 30, 39, 29, 10, 13];

console.log(array1.every(isBelowThreshold)); // true

some()

const array = [1, 2, 3, 4, 5];

const even = (element) => element % 2 === 0;

console.log(array.some(even)); // true

reduce()

const array1 = [1, 2, 3, 4];
const reducer = (accumulator, currentValue) => accumulator + currentValue;

// 1 + 2 + 3 + 4
console.log(array1.reduce(reducer)); // 10

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