function cmnt(trailingLine) {
        var ret = null;
        if (trailingLine === undefined) {
            if (commentLine === line - 1 && (alternateCommentMode || commentType === "*" || commentLineEmpty)) {
                ret = commentText;
            }
        } else {
            /* istanbul ignore else */
            if (commentLine < trailingLine) {
                peek();
            }
            if (commentLine === trailingLine && !commentLineEmpty && (alternateCommentMode || commentType === "/")) {
                ret = commentText;
            }
        }
        return ret;
    }
Gets a comment.
@param {number} [trailingLine] Line number if looking for a trailing comment
@returns {string|null} Comment text
@inner