Node.js Basics — HTTP

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Node.js is a popular runtime platform to create programs that run on it.

It lets us run JavaScript outside the browser.

In this article, we’ll look at how to start using Node.js to create programs.

HTTP

The http module is a module that comes with the Node.js runtime environment.

We can use it to create a simple HTTP server.

All we have to do is to require the HTTP package by writing:

const http = require('http');
const server = http.createServer();
server.listen(8080, () => {
  console.log( 'Listening on port 8080' );
});

We require the HTTP module and then call the createServer method on the imported module to create our server.

Then we call the listen method on the server object to listen for requests on port 8080.

If we want to to handle requests and return responses, we can use the request and response parameters to get the request data and create the response respectively.

For example, we can write:

const http = require('http');
let count = 0;
const server = http.createServer((request, response) => {
  count += 1;
  response.writeHead(201, {
    'Content-Type': 'text/plain'
  });
  const message = `count: ${count}`;
  response.end(message);
});
server.listen(8080, () => {
  console.log('Listening on port 8080');
});

We use the methods in the response object to create the response that we return to the user.

We call the writeHead method with the status code and the response headers that we want to return.

The Content-Type header is set to text/plain so that we can let the client know what the data type of the response is.

201 status means a new object is created.

The response.end method lets us return the response body to the client.

To get request data, we can use the properties of the request parameter.

For example, we can write:

const http = require('http');
let count = 0;
const server = http.createServer((request, response) => {
  count += 1;
  response.writeHead( 201, {
    'Content-Type': 'text/plain'
  });
  const message = `count: ${count}, path: ${request.url}`;
  response.end(message);
});
server.listen(8080, () => {
  console.log('Listening on port 8080');
});

to get the path of the URL with the request.url property and return it with the response body.

Routing

Since we have access to the URL that the request is made to, we can do something according to the URL that the user is accessing.

For example, we can write:

const http = require('http');
let count = 0;
const server = http.createServer((request, response) => {
  let message,
    status = 200;
  count += 1;
  switch (request.url) {
    case '/count':
      message = count.toString();
      break;
    case '/hello':
      message = 'World';
      break;
    default:
      status = 404;
      message = 'Not Found';
      break;
  }
  response.writeHead(status, {
    'Content-Type': 'text/plain'
  });
  response.end(message);
});
server.listen(8080, () => {
  console.log('Listening on port 8080');
});

to send different responses according to the URL that is given.

If request.url is /count then we return the value of the count with the 200 status.

If request.url is /hello , then we return 'World' with the 200 status.

Otherwise, we return 'Not Found' with a 404 status.

Conclusion

We can create a simple HTTP server with the Node.js’s built-in http module.