Category: JavaScript Answers

To use multiple parameters in URL in Node.js Express, we add multiple parameter placeholders.

For instance, we write

app.get("/fruit/:fruitName/:fruitColor", (req, res) => {
  const data = {
    fruit: {
      apple: req.params.fruitName,
      color: req.params.fruitColor,
    },
  };

  send.json(data);
});

to add the fruitName and fruitColor URL placeholders for the get route.

Then we get their values from the req.params object.

To start a Node.js server as a daemon process, we use the forever package.

For instance, we run

npm install -g forever

to install forever globally.

Then we run it by running

forever start server.js

We run server.js as a daemon with forever start.

To fix "Cannot find module ‘ts-node/register’" error with JavaScript, we install the ts-node package.

To install it, we run

npm install ts-node --save-dev

to save the ts-node package as a dev dependency.

To fix nodemon not found in npm with JavaScript, we install nodemon.

To install it, we run

npm install nodemon --save 

Then we add

{
  //...
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon app.js"
  }
  //...
}

in package.json to add the start script to run app.js with nodemon.

Then we run

npm start

to start the script.

To use socket.io in Express 4 and express-generator’s /bin/www with JavaScript, we create a module with the socket.io code.

For instance, we write

const io = require("socket.io")();
const socketApi = {
  io,
};

io.on("connection", (socket) => {
  console.log("A user connected");
});

module.exports = socketApi;

in socketApi.js to listen for client connections by call on with 'connection' and the event handler.

We export the socketApi object with the io object.

Then we write

const app = require("../app");
const debug = require("debug")("socketexpress:server");
const http = require("http");
const socketApi = require("../socketApi");

const port = normalizePort(process.env.PORT || "3000");
app.set("port", port);

const server = http.createServer(app);
socketApi.io.attach(server);

to import the socketApi file with require("../socketApi").

Then we call socketApi.io.attach to attach the Express server to it.