_.contains = function(obj, item, fromIndex, guard) {
    return _.indexOf(obj, item, fromIndex) >= 0;
  };

_.indexOf = createIndexFinder(1, _.findIndex, _.sortedIndex);

function createIndexFinder(dir, predicateFind, sortedIndex) {
    return function(array, item, idx) {
      var i = 0, length = getLength(array);
      for (idx = dir > 0 ? i : length - 1; idx >= 0 && idx < length; idx += dir) {
        if (array[idx] === item) return idx;
      }
      return -1;
    };
}