commonCharacters.js

/**
 * Write a function `f(a, b)` which takes two strings as arguments and returns a
 * string containing the characters found in both strings (without duplication), in the
 * order that they appeared in `a`. Remember to skip spaces and characters you
 * have already encountered!
 *
 * Example: commonCharacters('acexivou', 'aegihobu')
 * Returns: 'aeiou'
 *
 */

var commonCharacters = function(string1, string2) {
var result = [];
var charactersOfString1 = [];
for (var i = 0; i < string1.length; i++) {
  charactersOfString1.push(string1[i]);
}
for (var j = 0; j < charactersOfString1.length; j++) {
  if (string2.includes(charactersOfString1[j])) {
    if (!result.includes(charactersOfString1[j])) {
    result.push(charactersOfString1[j]);
    }
  }
}
return result.join('');
};