Javascript forEach, map, filter, some, every, reduce

★ 모든 method는 지정한 배열 내 요소들로 진행

array.map(x => x *2)이면 이때 x는 array[0], array[1].... 이 되는 것! 

// Array.map(함수)
const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];

const doubles = numbers.map(function (num) {
    return num * 2;
})

console.log(doubles)

///////////////////////////////////////////////////////////////
// Array.forEach(함수)
const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];

numbers.forEach(function (el) {
    if (el % 2 === 0) {
        console.log(el)
    }
})

///////////////////////////////////////////////////////////////
// Array.filter(함수)
const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];

numbers.filter(n => {
    return n < 10
})

///////////////////////////////////////////////////////////////
// Array.some(함수) & Array.every(함수)
const exams = [80, 98, 92, 78, 77, 90, 89, 84, 81, 77]

exams.every(score => score >= 80)
exams.some(score => score >= 75)

///////////////////////////////////////////////////////////////
// Array.reduce()
const prices = [9.99, 1.50, 19.99, 49.99, 30.50];

let total = 0;
for (let price of prices) {
    total += price
}
console.log(total)

const total = prices.reduce((total, price) => {
    return total + price
})