JSFiddle - React, Tailwind, and code Playground

JavaScript

var serial_maker = function() 
{
// Produce an object that produces unique strings. A
// unique string is made up of two parts: a prefix
// and a sequence number. The object comes with
// methods for setting the prefix and sequence
// number, and a gensym method that produces unique
// strings.
    var prefix = '';
    var seq = 0;
    return {
        set_prefix: function (p) {
            prefix = String(p);
        },
        set_seq: function (s) {
            seq = s;
        },
        gensym: function() {
            seq += 1; //supposedly should be here
            var result = prefix + seq;
            return result;
        }
    };
}();

var seqer = serial_maker;
seqer.set_prefix('Q');
seqer.set_seq(1000);
var unique = seqer.gensym();
alert(unique);