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NodeJS: How To Add Additional Middleware To Our Express Server

Intro

So we installed NodeJS on our machine.

We also learned how to create a simple server using express.

Now we want to learn how to add additional middleware to our express server.

Reuse our simple server from the last article

  • Open your terminal
  • Create a file named index.js:
touch index.js
  • Add this JavaScript code into it:
const express = require("express");
const app = express();

const PORT = 8080;

app.get("/", (request, response) => {
  response.send("Hello World");
});

app.listen(PORT, () => {
  console.log(`Server running at: http://localhost:${PORT}/`);
});

Note: This is our starting point, we have one working route. I updated req to request & res to response to increase readability.


Additional Middleware

What is Middleware?

Sometimes you want to add additional functionality between the default request-response-cycle. Let’s say you want to get some detailed information about the current request.

You can write a simple middleware, that handles this task, and add it to your express app.

Create a Middleware

  • Create a file named logger.js:
touch logger.js
  • Add this JavaScript code into it:
const logger = (req, res, next) => {
  console.log(
    `Time: ${new Date()} - Method: ${req.method} - Path: ${req.originalUrl}`
  );
  next();
};

module.exports = logger;
  • Require the new logger in index.js and use the middleware:
// import express (after npm install express)
const express = require("express");

// import the logger
const logger = require("./logger");

// create new express app and save it as app
const app = express();

// server configuration
const PORT = 8080;

// use the middleware
app.use(logger);

// create a route for the app
app.get("/", (req, res) => {
  res.send("Hello World");
});

// make the server listen to requests
app.listen(PORT, () => {
  console.log(`Server running at: http://localhost:${PORT}/`);
});

Run it from the terminal

  • Run it:
node index.js
Server running at: http://localhost:8080/
Time: Tue Sep 03 2019 17:32:30 GMT+0200 (Central European Summer Time) - Method: GET - Path: /

Further Reading


Questions

  • What’s your favorite middleware for express?