1
a = [1, 3, 45, 2, 10]
2

3
a.forEach((element, index) => {
4
  console.log(element, index)
5
})
6

7
// 1 0
8
// 3 1
9
// 45 2
10
// 2 3
11
// 10 4

1
const str = 'Hello World'
2
const ret = str.split(' ')
3
console.log(ret) // [ 'Hello', 'World' ]
4
const a = ret.join(' 뭐시기 ')
5
console.log(a) // Hello 뭐시기 World

1
let numbers = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
2
numbers = numbers.sort((a, b) => a - b) // 오름차순
3
console.log(numbers) // [(1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 9)]
4

5
numbers = numbers.sort((a, b) => (a - b) * -1) // 내림차순
6
console.log(numbers) // [(9, 6, 5, 5, 5, 4, 3, 3, 2, 1, 1)]

1
const numbers = [1, 2, 3, 4, 5, 6]
2
const ret = numbers.filter(ele => ele % 2 === 0)
3
console.log(ret) // [2, 4, 6]

1
const numbers = [1, 2, 3, 4, 5]
2
const ret = numbers.map(el => el * 2)
3
console.log(ret) // [ 2, 4, 6, 8, 10 ]

1
const numbers = [1, 2, 3, 4, 5]
2
let b = []
3
for (let a of numbers) {
4
  b.push(a * 2)
5
}
6
console.log(b) // [ 2, 4, 6, 8, 10 ]

1
const numbers = [1, 2, 3, 4, 5]
2
const ret = numbers.reduce((total, element) => total + element, 0)
3
console.log(ret) // 15

1
flowchart LR
2
    1 --> 2
3
    1 --> 3
4
    2 --> 4
5
    3 --> 4
6
    3 --> 5

1
const graph = {
2
  1: [2, 3],
3
  2: [4],
4
  3: [4, 5],
5
  4: [],
6
  5: [],
7
}
8

9
const dfs = (here, visited = new Set()) => {
10
  if (visited.has(here)) return
11
  visited.add(here)
12
  console.log(here)
13
  graph[here].forEach(el => dfs(el, visited))
14
}
15

16
dfs(1)
17
// 1
18
// 2
19
// 4
20
// 3
21
// 5

1
const a = [1, 2, 3, 4, 5, 6, 7, 8]
2
const bs = () => {
3
  let lo = 0
4
  let hi = a.length - 1
5
  const target = 3
6

7
  while (lo <= hi) {
8
    let mid = Math.floor((lo + hi) / 2)
9
    if (a[mid] == target) {
10
      console.log(target)
11
      return '찾았다'
12
    } else if (a[mid] > target) {
13
      hi = mid + 1
14
    } else {
15
      first = mid + 1
16
    }
17
  }
18
  return -1
19
}
20

21
const ret = bs() // 3
22
console.log(ret)

1
// 모든 원소가 0인 1차원배열
2
let a = Array(50).fill(0)
3
// console.log(a)
4

5
// 모든 원소가 1인 2차원배열
6
let b = Array(5)
7
  .fill()
8
  .map(el => Array(5).fill(1))
9
console.log(b)

1
const fibo = (idx, memo = {}) => {
2
  if (idx <= 2) return 1
3
  if (idx in memo) return memo[idx]
4
  memo[idx] = fibo(idx - 1, memo) + fibo(idx - 2, memo)
5
  return memo[idx]
6
}
7
const ret = fibo(10)
8
console.log(ret) // 55 => 1, 1, 2, 3, 5, 8, 13, 21, 34, 55

1
const arr = [1, 2, 3, 4, 5]
2
;[arr[1], arr[3]] = [arr[3], arr[1]]
3
console.log(arr) // [ 1, 4, 3, 2, 5 ]