Back End Development and APIs Projects - URL Shortener Microservice

In replit, I constantly get an error message saying I got NaN for short_url which doesn’t allow me to pass the test.

I checked my code very carefully again and again, there’s no chance for short_url to get NaN. I test my code with differnt urls, both ones exsiting in datebase and ones not, I got the expected reponse to the post request and expected result in database. I never got NaN for short_url when I test it manually. So What should I do to get this test past?

const express = require('express');
const cors = require('cors');
const app = express();
const mongoose = require('mongoose');
const bodyParser = require('body-parser');
const dns = require('dns');

mongoose.connect(process.env.MONGO_URL, {
  useUnifiedTopology: true,
  useNewUrlParser: true

const urlSchema = new mongoose.Schema({
  original_url: {type: String, required: true },
  short_url: {type: Number}

const Url = mongoose.model("Url", urlSchema);
const port = process.env.PORT || 3000;

app.use(bodyParser.urlencoded({ extended: false }));
app.use('/public', express.static(`${process.cwd()}/public`));

app.get('/', function (req, res) {
  res.sendFile(process.cwd() + '/views/index.html');

// Your first API endpoint'/api/shorturl', (req, res) => {
  let fixedUrl="";
  } else {
    fixedUrl=fixedUrl.substring(0, fixedUrl.length-1);
   dns.lookup(fixedUrl, async(err, address) => {
    if (err) {
      res.json({ error: "invalid url" });
    } else {
      const foundDoc =await Url.findOne({ original_url: req.body.url });
      if (!foundDoc) {
        let lastDoc =await Url.find().sort({ short_url: -1 }).limit(1);
        let newUrl={};
        if (lastDoc.length===0) {
          newUrl={original_url:req.body.url, short_url:1};
        } else {
          let lastShort=lastDoc[0].short_url;
          newUrl={original_url:req.body.url, short_url:lastShort*1+1};
        const result=await Url.create(newUrl);
        res.json({original_url:result.original_url, short_url:result.short_url});  
      } else {
        res.json({original_url:foundDoc.original_url, short_url:foundDoc.short_url});

  const index=req.params.index*1;
  const foundDoc=await Url.findOne({short_url:index});
    res.json({error:'invalid url'});
  } else {

app.listen(port, function () {
  console.log(`Listening on port ${port}`);

Your project link(s)

solution: boilerplate-project-urlshortener-2 - Replit

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Challenge: Back End Development and APIs Projects - URL Shortener Microservice

Link to the challenge:

You need to add some console.log statements to figure out why your app treats:

as an invalid url (when it should not).

Thanks. Finally I sorted it our with your reminding. My code can only handle url without any routes in it. The fourth requirement of this test confuses people a little bit. It gives us an example of “”. I thought we need to handle hostname of urls only.

Yesterday, I mannually tested with tens of urls and all got expected results, but none of them with routes in it.

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