In this blog, I will show you how to create a NodeJS server using core http module. We will create a simple server that will serve static assets and a simple API to return some JSON data.
\nIn the process, you will also learn about the request and response objects provided by NodeJS, which are used by every other framework built on top of NodeJS like ExpressJS etc.
\nWith that in mind, let's begin.
\nCreate a folder by any name and initialize a node project in it using npm init -y
package.json file in your directory.server.js in your directory.public at the root of your project.Add a file named index.html with the following content\nindex.html
<!DOCTYPE html>\n<html lang="en">\n<head>\n <meta charset="UTF-8">\n <meta name="viewport" content="width=device-width, initial-scale=1.0">\n <title>Demo</title>\n</head>\n<body>\n <h1>Coming from the Root </h1>\n</body>\n</html>Now we will create a node server that will serve our index.html file when a request is sent to /.
server.js
const http = require('http');\n const path = require('path');\n const fs = require('fs');\n const PORT = 3000;\n const hostname = 'localhost';\n\n // createServer is the http method used to create a web server that takes a callback.\n const server = http.createServer(serverHandler);\n\n // callback function definition\n function serverHandler(req, res) => {\n if(req.method === 'GET' && req.url === '/') {\n let filePath = path.resolve(__dirname, 'public/index.html')\n let fileExists = fs.existsSync(filePath);\n if (!fileExists) {\n res.statusCode = 404;\n res.setHeader('Content-Type', 'text/html');\n res.end(`\n <html>\n <body>\n <h3>Page not found</h3>\n </body>\n </html>`)\n } else {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/html');\n fs.createReadStream(filePath).pipe(res);\n }\n }\n }\n\n server.listen(PORT, hostname, () => {\n console.log(`Server running at ${hostname}:${PORT}`); \n })Let's understand what just happened in the above code snippet:
\ncreateServer method provided by node http module. createServer takes a callback which will be called when there is an incoming request with req and res parameters.serverHandler, we have used an if block to check if the incoming request is a GET request and the request url is / then code inside if statement will be executed.index.html which we want to serve exists or not in our public directory using existsSync, which synchronously checks for the file at the given path and returns true if the file exists.createReadStream method from fs module and pipe it into res object which sends it to the browser.server.listen to start our server on the PORT 3000.Now it's time to test our server. Run node server.js at the root of the project, and you will see the server running on PORT 3000.\nOpen your browser and enter localhost:3000 in the address bar, and you will get the HTML response.
Now we will expand our callback, which we passed to createServer to handle one more GET request at /notes, which will return an array of notes to the browser.
Update the serverHandler function with the following code snippet in your server.js file
server.js
...\n function serverHandler(req, res) {\n if(req.method === 'GET' && req.url === '/') {\n let filePath = path.resolve(__dirname, 'public/index.html')\n let fileExists = fs.existsSync(filePath);\n if (!fileExists) {\n res.statusCode = 404;\n res.setHeader('Content-Type', 'text/html');\n res.end(`\n <html>\n <body>\n <h3>Page not found</h3>\n </body>\n </html>`)\n } else {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/html');\n fs.createReadStream(filePath).pipe(res);\n }\n }\n // Newly added code \n if (req.method === 'GET' && req.url === "/notes") {\n const notes = [\n {\n id: 1,\n title: "Demo Note"\n },\n {\n id: 2,\n title: "Another Note"\n }\n ]\n\n res.statusCode = 200;\n res.setHeader('Content-Type', 'application/json');\n res.end(JSON.stringify(notes));\n } else {\n res.setHeader('Content-Type', 'application/json')\n res.end(JSON.stringify({message: `${req.method} is not supported for ${req.url}`}))\n } \n }\n ...if statement to handle the request coming at /notes .application/json for the browser to process it accordingly.With that, we have created a simple node server to serve static content as well a simple API to return JSON data.
\nWe saw how we had to handle each request with its method and the URL. With an increasing number of routes, such things become hard to manage as we will have to add multiple if statements. And that's why frameworks like ExpressJS, HapiJS exist, which makes creating servers in NodeJS very easy. But it's important to know what happens under the hood as there is no magic happening in those frameworks.
\nThe complete code for this blog can be found at Github Repo.
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