index.js

const fs = require('fs');
const http = require('http');
const url = require('url');

// Using syncchronous here because this only gets read when the server stard
// read the json data
const json = fs.readFileSync(`./city.list.json`, 'utf-8');

// parse the json data into an array
const locationData = JSON.parse(json);

// Creating server with http package
const server = http.createServer((req, res) => {
  // get the path name using the url package
  const pathName = url.parse(req.url, true).pathname;
  // get what is sent on the url q parameter, for example www.url.com/?q=aveiro
  const name = url.parse(req.url, true).query.q;

  // --- ROUTES ---
  // if route equals root and there is data on the name variable
  if (pathName === '/' && name) {
    // filter the json file to save on the results variable what matches the query made
    const results = locationData.filter(item => {
      // regex to search for case insensitive data
      const regex = new RegExp(name, 'gi');
      return item.name.match(regex) || item.country.match(regex);
    });
    const filtered = results.filter(
      (location, i, self) =>
        i ===
        self.findIndex(
          t => t.name === location.name && t.country === location.country
        )
    );
    // if nothing matches
    if (results.length === 0) {
      res.writeHead(404, { 'Content-type': 'text/html' });
      res.end('Url was not found on the server!');
    }
    // if matches, return json data
    else {
      res.writeHead(200, { 'Content-type': 'application/json' });
      res.end(JSON.stringify(filtered));
    }
  } else {
    res.writeHead(404, { 'Content-type': 'text/html' });
    res.end('Url was not found on the server!');
  }
});

// Listen for server on URL and PORT
const PORT = process.env.PORT || 1337;
server.listen(PORT, () => {
  console.log('Listening for requests now.');
});