Function peek

js/SCAST.js:205–207

()

            input.croak(`Can't handle character :${ch}(${ch.charCodeAt(0)})`);
        }
        function peek() {
            return current || (current = read_next());//after next() not call peek()
        }
        function next() {
            var tok = current;
            if(current?.type=='id')prev_id=current;