In Node.js, we manually create a server that lives in the backend of our website. This server actively listens for requests from the browser and responses to them.
Firstly, we’ll need to import the http node core module:
const http = require("http");
Then, we use the http.createServer() method, which takes in a callback function as an argument. This callback function runs every time a request comes in.
The callback function has two objects:
const server = http.createServer((req, res) => {
console.log("request was made");
});
To make the server actively listen to the requests, we need to invoke the listen method server.listen() and pass in 3 arguments:
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
To send a response to the browser, we need the following steps:
setHeader(). It’ll give the browser the type of response coming back to it (text, HTML, JSON, etc.).Example: Response a plain text
const http = require("http");
const server = http.createServer((req, res) => {
console.log("request was made");
// Set header content type
res.setHeader("Content-Type", "text/plain");
// Write and end response
res.write("Hello, world");
res.end();
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
So if we open http://localhost:3000/, we’ll see the text “Hello, world”.
Example: Response HTML
const http = require("http");
const server = http.createServer((req, res) => {
console.log("request was made");
// Set header content type
res.setHeader("Content-Type", "text/html");
// Write and end response
res.write("<p>Hello, world</p>");
res.write("<p>Hello, again</p>");
res.end();
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
In this section, we’ll learn how to send a complete HTML page to the browser.
For example, we have an HTML file:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width,initial-scale=1" />
<title lang="en-US">Node.js Web server</title>
</head>
<body>
<h1>Node.js Web server</h1>
<p>This is a paragraph.</p>
</body>
</html>
In our server.js file, we will need to import the fs module and read the HTML file:
const http = require("http");
const fs = require("fs");
const server = http.createServer((req, res) => {
console.log("request was made");
// Set header content type
res.setHeader("Content-Type", "text/html");
// Send an HTML file
fs.readFile("./views/index.html", (err, data) => {
if (err) {
console.log(err);
res.end();
} else {
res.write(data);
res.end();
}
});
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
If we only send one thing to the res.write(), we can directly send it to the res.end() method.
const http = require("http");
const fs = require("fs");
const server = http.createServer((req, res) => {
console.log("request was made");
res.setHeader("Content-Type", "text/html");
fs.readFile("./views/index.html", (err, data) => {
if (err) {
console.log(err);
res.end();
} else {
// res.write(data);
res.end(data);
}
});
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
We can use switch to provide basic routing for a website.
For example, we’ll send users to the About page if they access /about and the 404 page if they access non-exist pages.
const http = require("http");
const fs = require("fs");
const server = http.createServer((req, res) => {
console.log("request was made");
// Set header content type
res.setHeader("Content-Type", "text/html");
// Routing
let path = "./views/";
switch (req.url) {
case "/":
path += "index.html";
break;
case "/about":
path += "about.html";
break;
default:
path += "404.html";
}
// Send Html
fs.readFile(path, (err, data) => {
if (err) {
console.log(err);
res.end();
}
res.end(data);
});
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
The status code describes the type of response sent to the browser. They are in the range of 100 to 500:
The most common status codes are:
To set the status code for responses, we use res.statusCode:
const http = require("http");
const fs = require("fs");
const server = http.createServer((req, res) => {
console.log("request was made");
// Set header content type
res.setHeader("Content-Type", "text/html");
// Routing
let path = "./views/";
switch (req.url) {
case "/":
path += "index.html";
res.statusCode = 200;
break;
case "/about":
path += "about.html";
res.statusCode = 200;
break;
default:
path += "404.html";
res.statusCode = 404;
}
// Send html
fs.readFile(path, (err, data) => {
if (err) {
console.log(err);
res.end();
}
res.end(data);
});
});
server.listen(3000, "localhost", () => {
console.log("listening for request");
});
To redirect one page to another, we use the setHeader() method.
For example, we no longer have the /about-us page, so we redirect it to /about page.
case "/about-us":
res.statusCode = 301;
res.setHeader("Location", "/about");
res.end();
break;