Help creating short url

I’m trying to make ‘URL Shortener’, and I’m wondering if the short URL have to be a value from an internal counter or can it be anything else? Because I have been trying to make a counter and put the count value as the short url, but I’m struggling making it work.

//create counter schema
const CounterSchema = new mongoose.Schema({
  _id: { type: String, require: true },
  sequence: { type: Number, require: true}

var counter = mongoose.model('counter', CounterSchema);

//create url schema
const UrlSchema = new mongoose.Schema({
  original_url: { type: String, require: true},
  count: { type: Number, require: false}

UrlSchema.pre('save', function(next) {
  var doc = this;
    {_id: 'original_url'},
    { $inc: {sequence: 1} },
    { new: true },
    function(err, count) {
      if(err) return next(err);
      doc.count = count.sequence;

var URL = mongoose.model('URL', UrlSchema);
// your first API endpoint...
app.get("/api/shorturl/:code", function(req, res) {
  const urlCode = req.params.code;
  URL.findOne({ short_url: urlCode}, function(err, doc) {
    if(err) { return console.error(err) };
});"/api/shorturl/new", function (req, res) {
  const originalUrl = req.body.url;
  const host = originalUrl.replace(/^(?:https?:\/\/)?(?:www\.)?/i, "").split('/')[0]; //(change from url to host name)
  //validate url, dns lookup
  dns.lookup(host, function(err) {
    if(err) { 
      res.json({error: 'invalid URL'});
    else { 
      //findOne url
      URL.findOne({original_url: originalUrl}, function(err, url) {
      if(err) { return console.error(err) };
      //if url exists in db show json
      if(url) { 
      //if url does not exists in db, save data to server
      else { 
        const url = new URL({ original_url: originalUrl});
          res.send({ original_url: originalUrl })


It can be a hash generated from the url or just an index that you could search for, number of registered + 1 or something like that.

I used a Hash in mine, I’m having some issues with redirection if you know something about that could help… my url it being concatenated as an extension of my current route.