Q.

Consider an array/list of sheep where some sheep may be missing from their place. We need a function that counts the number of sheep present in the array (true means present).

For example,

[true, true, true, false,
true, true, true, true ,
true, false, true, false,
true, false, false, true ,
true, true, true, true ,
false, false, true, true]
The correct answer would be 17.

Hint: Don't forget to check for bad values like null/undefined

A)

function countSheeps(arrayOfSheep) {
  let count = 0;
  if (arrayOfSheep === null)
    return 0;
  else {
    for (let el of arrayOfSheep)
      if (el === true)
        count++;
  }
  return count;
}

other

.filter Boolean을 사용하여 간결하게 나타내는 방법도 있다. 정말 자바스크립트의 메소드는 알면 알수록 끝이 없는 것 같다.🙈

function countSheeps(arr) {
  return arr.filter(Boolean).length;
}