docs: function arrayContainsBefore(array, element, index, keyFn) {
      var i = -1;
  
      if (keyFn) {
        keyFn = createCallback(keyFn);
        while (++i < index) {
          if (keyFn(array[i]) === keyFn(element)) {
            return true;
          }
        }
  
      } else {
        while (++i < index) {
          if (array[i] === element) {
            return true;
          }
        }
      }
  
      return false;
    }