How do I keep spaces in a string?

Question

I am working with a substitution cipher, where each letter of the alphabet is represented by a letter from the substituted alphabet.

function substitution(input, alphabet) {
  let str = '';
  let result = input.split('');
  alphabet = alphabet.split('');

  for (let i = 0; i < result.length; i++) {
    if (alphabet.includes(result[i])) {
      str += alphabet[i];
      console.log(str);
    }
  }
  //console.log(str);
  return str;
}

substitution('ab c', 'plmoknijbuhvygctfxrdzeswaq');

The output I'm expecting is 'pl m' , however I am getting 'plo' as the space moves to the next letter since there isn't a space in the substituted alphabet. Is there a way to preserve that space without using regex?

Answer 1

If the letter is in your alphabet, you add the encrypted letter. But if it's not in the alphabet, you don't do anything. You should still add it, just not encrypted:

function substitution(input, alphabet) {
  let str = '';
  let result = input.split('');
  alphabet = alphabet.split('');

  for (let i = 0; i < result.length; i++) {
    if (alphabet.includes(result[i])) {
      str += alphabet[i];
      console.log(str);
    } else {
      str += result[i];
    }
  }
  //console.log(str);
  return str;
}

substitution('ab c', 'plmoknijbuhvygctfxrdzeswaq');

Answer 2

I'd use a regular expression instead - match and replace word characters. Use a replacer function that returns the index of the match count on the string, and increments the match count:

 function substitution(input, alphabet) { let i = 0; return input.replace( /\w/g, () => alphabet[i++] ); } console.log(substitution('ab c', 'plmoknijbuhvygctfxrdzeswaq'));