function findRight(arr, f, opt_obj) {
  const i = findIndexRight(arr, f, opt_obj);
  return i < 0 ? null : typeof arr === 'string' ? arr.charAt(i) : arr[i];
}
Search an array (in reverse order) for the last element that satisfies a
given condition and return that element.
@param {IArrayLike<T>|string} arr Array or array
    like object over which to iterate.
@param {?function(this:S, T, number, ?) : boolean} f The function to call
    for every element. This function
    takes 3 arguments (the element, the index and the array) and should
    return a boolean.
@param {S=} opt_obj An optional "this" context for the function.
@return {T|null} The last array element that passes the test, or null if no
    element is found.
@template T,S