fp flavored solutions for https://youtu.be/XlI1zoH2gjU

unriddle_me_1.ts

const unriddle_me_1 = (str: string): string => {
  const length = Math.ceil(str.length / 2);
  const [a, b] = [str.slice(0, length), str.slice(length)];

  return a.split('').reduce((acc, curr, idx) => {
    return acc + curr + (b[idx] || '');
  }, '');
};

console.log(
  unriddle_me_1('Wligo ae n eeoigsfwrakn nwtraddvlpn otae'),
);

unriddle_me_2.ts

const unriddle_me_2 = (str: string): string => {
  return str.split('').reduce((acc, curr, idx) => {
    return idx % 2 ? acc : acc + curr;
  }, '');
};

console.log(
  unriddle_me_2(
    'f rqofmv fa  gstpheuc ikfuiyctaqtaixocnv fagrhey  euaksiy',
  ),
);

unriddle_me_3.ts

const unriddle_me_3 = (str: string): string => {
  return str
    .slice(2)
    .split('')
    .reduce((acc, curr, idx) => {
      return idx % 3 ? acc : acc + curr;
    }, '');
};

console.log(
  unriddle_me_3(
    ` gihjfkl oib 4o6jtaxhdb gha trh?e't r3fesrqqoa zs efgngy.`,
  ),
);