Switch statement returning undefined

Question

function getLetter(s) {
    let letter = s[0];
    // Write your code here
    let A = ['a','e','i','o','u'];
    let B = ['b','c','d','f','g'];
    let C = ['h','j','k','l','m'];
    let D = ['n','p','q','r','s','t','v','w','x','y','z'];

  switch(letter) {
    case A.includes(s.charAt(0)): 
      return 'A';
    break;

    case B.includes(s.charAt(0)): 
      return 'B';
    break;

    case C.includes(s.charAt(0)): 
      return 'C';
    break;

    case D.includes(s.charAt(0)): 
        return 'D';
    break;
  }
}

s = 'adam';
t = getLetter(s);
console.log(t);

I'm learning switches and I'm trying this problem where I'm supposed to pass in a string and the function getLetter() is supposed to return 'A' if the first letter of the string is any of the elements in array A. And similar for arrays B,C,D. I tried the code above but it returns undefined. What am I doing wrong?

Answer 1

You need to check against a boolean value, like true , because you use includes , which returns true or false .

BTW, by using return in each case , you could omit to break , because the function exits with return , which exits the switch statement as well.

 function getLetter(s) { let letter = s[0]; // Write your code here let A = ['a', 'e', 'i', 'o', 'u']; let B = ['b', 'c', 'd', 'f', 'g']; let C = ['h', 'j', 'k', 'l', 'm']; let D = ['n', 'p', 'q', 'r', 's', 't', 'v', 'w', 'x', 'y', 'z']; switch (true) { // <-- boolean value with strict comparison === case A.includes(letter): return 'A'; case B.includes(letter): return 'B'; case C.includes(letter): return 'C'; case D.includes(letter): return 'D'; } } var s = 'adam', t = getLetter(s); console.log(t);

Answer 2

You can use find instead of includes , when you pass a character to switch() it tries to match that against case, since includes return true/false so it won't match any case

 function getLetter(s) { let letter = s[0]; let A = ['a', 'e', 'i', 'o', 'u']; let B = ['b', 'c', 'd', 'f', 'g']; let C = ['h', 'j', 'k', 'l', 'm']; let D = ['n', 'p', 'q', 'r', 's', 't', 'v', 'w', 'x', 'y', 'z']; switch (letter) { case A.find(v => v === letter): return 'A'; case B.find(v => v === letter): return 'B'; case C.find(v => v === letter): return 'C'; case D.find(v => v === letter): return 'D'; } } s = 'adam'; t = getLetter(s); console.log(t);