nodejs json data serving

const userRoutes = (app, fs) => {
  // variables
  const dataPath = './data/users.json';

  // READ
  app.get('/users', (req, res) => {
    fs.readFile(dataPath, 'utf8', (err, data) => {
      if (err) {
        throw err;
      }

      res.send(JSON.parse(data));
    });
  });
};

module.exports = userRoutes;
const userRoutes = (app, fs) => {
  //...unchanged ^^^

  // refactored helper methods
  const readFile = (
    callback,
    returnJson = false,
    filePath = dataPath,
    encoding = 'utf8'
  ) => {
    fs.readFile(filePath, encoding, (err, data) => {
      if (err) {
        throw err;
      }

      callback(returnJson ? JSON.parse(data) : data);
    });
  };

  const writeFile = (
    fileData,
    callback,
    filePath = dataPath,
    encoding = 'utf8'
  ) => {
    fs.writeFile(filePath, fileData, encoding, err => {
      if (err) {
        throw err;
      }

      callback();
    });
  };

  // READ
  // Notice how we can make this 'read' operation much more simple now.
  app.get('/users', (req, res) => {
    readFile(data => {
      res.send(data);
    }, true);
  });
};

module.exports = userRoutes;
{
  "1": {
    "name": "king arthur",
    "password": "password1",
    "profession": "king",
    "id": 1
  },
  "2": {
    "name": "rob kendal",
    "password": "password3",
    "profession": "code fiddler",
    "id": 2
  },
  "3": {
    "name": "teresa may",
    "password": "password2",
    "profession": "brexit destroyer",
    "id": 6
  }
}
// UPDATE
app.put('/users/:id', (req, res) => {
  readFile(data => {
    // add the new user
    const userId = req.params['id'];
    data[userId] = req.body;

    writeFile(JSON.stringify(data, null, 2), () => {
      res.status(200).send(`users id:${userId} updated`);
    });
  }, true);
});
// load up the express framework and body-parser helper
const express = require('express');
const bodyParser = require('body-parser');

// create an instance of express to serve our end points
const app = express();

// we'll load up node's built in file system helper library here
// (we'll be using this later to serve our JSON files
const fs = require('fs');

// configure our express instance with some body-parser settings
// including handling JSON data
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

// this is where we'll handle our various routes from
const routes = require('./routes/routes.js')(app, fs);

// finally, launch our server on port 3001.
const server = app.listen(3001, () => {
  console.log('listening on port %s...', server.address().port);
});
// load up our shiny new route for users
const userRoutes = require('./users');

const appRouter = (app, fs) => {
  // we've added in a default route here that handles empty routes
  // at the base API url
  app.get('/', (req, res) => {
    res.send('welcome to the development api-server');
  });

  // run our user route module here to complete the wire up
  userRoutes(app, fs);
};

// this line is unchanged
module.exports = appRouter;