function trimmedRightIndex(string) {
    var index = string.length;

    while (index-- && isWhitespace(string.charCodeAt(index))) {}
    return index;
  }
Used by `_.trim` and `_.trimRight` to get the index of the last non-whitespace
character of `string`.

@private
@param {string} string The string to inspect.
@returns {number} Returns the index of the last non-whitespace character.