index.js (url shortener)

require('dotenv').config();
const express = require('express');
const cors = require('cors');
const app = express();
const dns = require('dns')
const bodyParser = require('body-parser')
const mongoose = require("mongoose")
//var router = express.Router();

// Basic Configuration
const port = process.env.PORT || 3000;

mongoose.connect(process.env.MONGO_URI, { useNewUrlParser: true, useUnifiedTopology: true });
//throw error if connection isnt met
const db = mongoose.connection;
db.on("error", console.error.bind(console, "connection error: "))
db.once("open", () =>{
  console.log("Connected successfully")
})

app.use(cors());

app.use('/public', express.static(`${process.cwd()}/public`));



const urlSchema = new mongoose.Schema({
  longUrl: {
    type: String,
    required: true,
  },
  shortUrl : {
    type: String
  }
})

const url = mongoose.model('url', urlSchema)

//generate alphanumeric value of four characters, check if this value exists in the database
const randomStr= () => {
  let val = Math.random().toString(16).slice(2,6)
  if (url.exists({shortUrl: val}) == null) {
  return val
}
  else{
  randomStr()
  } 
}

//create a shortened url from a link
const createUrl = (str) => {
    //check if url is valid
    dns.lookup(str, (error,    address, family) =>{
      if (error){
        console.log(error)
        return res.json({
          error: 'invalid url'
        })
      }
    })
    //check if original url does not exist in database
    if(url.exists({longUrl: str} === null)){
    url.create({longUrl: str, shortUrl: randomStr()})
      //verify process
      return True
    }
  else{
    return False
  }
    
}

//post request adding a url to the database
app.post("/api/shorturl", bodyParser.urlencoded({extended: false}), (req, res) => {
    if (createUrl(req.body) === true){
      createUrl(req.body)
      smallUrl = url.find({ longUrl: req.body}, 'shortUrl')
      res.json({longUrl: req.body, shortUrl: smallUrl 
    })
  }
})

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


// Your first API endpoint
app.get('/api/hello', function(req, res) {
  res.json({ greeting: 'hello API' });
});

app.get('/api/shorturl/:shorturl', (req,res) => {
  let link = req.params.shorturl
  
})

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

Console:
TypeError [ERR_INVALID_ARG_TYPE]: The "hostname" argument must be of type string. Received [Object: null prototype]
    at new NodeError (node:internal/errors:372:5)
    at validateString (node:internal/validators:120:11)
    at Object.lookup (node:dns:105:5)
    at createUrl (/home/runner/boilerplate-project-urlshortener/index.js:54:9)