12.js

// 1.2 Makovskyi
function search(needle, haystack) {
  var i = 0;
  var valueSearching = false;
  if (typeof haystack === 'object') {
    if (Array.isArray(haystack)) {
      for (; i < haystack.length; i++) {
        if (search(needle, haystack[i])) {
          return true;
        }
      }
    } else {
      Object.keys(haystack).some(function object(key) {
        if (search(needle, haystack[key])) {
          valueSearching = true;
          return true;
        }
        return false;
      });
      return valueSearching;
    }
  } else {
    if (needle === haystack) {
      return true;
    }
  }
  return false;
}

console.log(search(777, { a: [1, 2, { s: 4, c: { u: 5, mm: [{ findMe: 777 }, 7, 8] } }], s: 9 }));