Secret String

const recoverSecret = function (triplets) {
  // const flattened = (arr) => [].concat(...arr);
  let secretLetters = filterDublicates(triplets.flat());
  const string = [];
  const haveItems = (nested) => nested.length;

  console.log(secretLetters);

  while (triplets.some(haveItems)) {
    let obj = returnObj(triplets);

    // filter last letter
    let [last] = secretLetters.filter(
      (l) => !Object.keys(obj).includes(l) && !string.includes(l)
    );

    // add to arr
    string.push(last);

    triplets.forEach((arr) => {
      arr.forEach((l, index) => {
        if (string.includes(l)) {
          arr.splice(index, 1);
          if (!arr.length) {
            arr = null;
          }
        }
      });
    });
  }

  return string.reverse().join('');

  // Declarations
  function returnObj(triplets) {
    const obj = {};

    triplets.forEach((triplet) => {
      triplet.forEach((letter, index) => {
        for (let i = 0, l = triplet.length; i < l; i++) {
          if (i > index) {
            if (!obj.hasOwnProperty(letter)) {
              obj[letter] = [];
            }

            obj[letter].push(triplet[i]);
          }
        }
      });
    });

    Object.keys(obj).forEach((key) => {
      obj[key] = filterDublicates(obj[key]);
    });

    return obj;
  }

  function filterDublicates(arr) {
    let filtered = [];

    arr.forEach((l) => {
      if (!filtered.includes(l)) {
        filtered.push(l);
      }
    });

    return filtered;
  }
};

let secret = 'whatisup';
const triplets1 = [
  ['t', 'u', 'p'],
  ['w', 'h', 'i'],
  ['t', 's', 'u'],
  ['a', 't', 's'],
  ['h', 'a', 'p'],
  ['t', 'i', 's'],
  ['w', 'h', 's'],
];

console.log(secret);
let result = recoverSecret(triplets1);
console.log('result:', result);