Node.js Code Snippets

If you want to take full advantage of Node.js, these are some of the most useful node.js code snippets for backend development.

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Coding in Node.js can be challenging and getting used to the intricacies of Node.js code can be quite confusing. This collection of Node.js code  examples is aimed at helping you perform common Node.js functions. No matter your experience level, from beginner to advanced, the following Node.js sample code will be useful for all developers. 

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How to Create a HTTP Server in Node.js

Tags: node.js, javascript, node server, web server

This Node.js code snippet creates a simple Node.js HTTP server that writes a response to the client and listens on port 8080. If it is running, a message will be logged stating "server running on port 8080".

const http = require('http');

http.createServer((request, response) => {

	response.writeHead(200, {
		'Content-Type': 'text/plain'
	});
	response.write('Hello from Pieces!');
	response.end();

}).listen(8080);

console.log('server running on port 8080'); 

Related links:

  1. Node HTTP tutorial
  2. Node.JS HTTP module

Node.js Parse command-line arguments

Tags: node.js, javascript, command-line arguments

This basic Node.js code is used to grab specified command-line arguments, we use the process module which gives control over the current Node.js process, and we remove the first two arguments from the command-line, the Node.js executable and the executed file name.

const getCmdArguments = () => process.argv.slice(2); 

Related links:

  1. How do I pass command line arguments to a Node.js program
  2. The argy property

How to use Sleep in Node.js

Tags: node.js, javascript, sleep, setTimeout

Implementing the sleep function in Node.js using setTimeout along with a dynamic argument specifying time to wait.

const sleep = ms => new Promise( res => setTimeout(res, ms)); 

Related links:

  1. Sleep in Node.js
  2. How to add Node.js Sleep function example

How to use the Assert function in Node.js

Tags: node.js, javascript, assert

The Assert Node.js example below uses the assert module to provide a set of assertion functions for verifying invariants.

const assert = require('assert');

assert(5 > 7); 

Related links:

  1. Assert function in node.js
  2. Node.js assert function

Getting the information of all CPUs installed

Tags: node.js, javascript, cpu

Get information about all CPUs available using the os module.

const os = require('os');
const value =  os.cpus();

console.log("os.cpus() ==> " + JSON.stringify(value) ); 

Related links:

  1. Node.js os cpus method
  2. Node.js Documentation v19.7.0 - OS
  3. Using os module in NodeJS

How to Store JSON in a File using Node.js

Tags: node.js, javascript, json

This Node.js code, given a data object, converts the object to a JSON string and stores it in a file with the specified path.

const fileSystem = require('fs')

const storeData = (data, path) => {
  try {
    fileSystem.writeFileSync(path, JSON.stringify(data))
  } catch (error) {
    console.error(error)
  }
} 

Related links:

  1. How to write a JSON object to file in Node.js

How to get data out of an HTTP Get Request using Node.js code snippets

Tags: node.js, javascript, HTTP

This simple Node.js code is used to get the data out of a Node.js HTTP get request with JavaScript, we can listen for the data event on the response and append it until the response has ended.

const callback = (response) => {
	let str = "";
	response.on("data", (chunk) => {
		str += chunk;
	});

	response.on("end", () => {
		console.log(str);
		// ...
	});
};

const request = http.request(options, callback).end(); 

Related links:

  1. 5 ways to make HTTP requests in Node.js
  2. How to get data out of a node.js HTTP get request

How to compare Two Buffers Using Node.js

Tags: node.js, javascript, buffer

Add this Node.js source code to compare two buffer objects and return a number defining their differences and can be used to sort arrays containing buffers.

const buffer1 = Buffer.from('abc');
const buffer2 = Buffer.from('abc');

let x = Buffer.compare(buf1, buf2);
console.log(x); 

Related links:

  1. Compare Two Buffers in Node.js
  2. Node.js Buffer.compare() Method - Node.js Syntax
  3. Node.js Buffer.compare() Method - Node.js example code

How to Create a static file server in Node.js

Tags: node.js, javascript, static file server

In this Node.js code example you request a given URL, the static file server will listen for requests and try to find a file on the local filesystem. If no file is found or it doesn’t exist, it returns a 404 error. The http module creates the server that listens on port 8000.

const fileSystem = require('fs');
const http = require('http');

http.createServer((request, response) => {
	fileSystem.readFile(__dirname + request.url, (error, data) => {
		if (error) {
			response.writeHead(404, {
				'Content-Type': 'text/html'
			});
			response.end('404: File not found');
		} else {
			response.writeHead(200, {
				'Content-Type': 'text/html'
			});
			response.end(data);
		}
	});
}).listen(8000); 

Related links:

  1. Serve Static Resources using Node-static Module
  2. How to create a simple web server that can read a given file on a given disk - readFile function

How to use Event emitter in Node.js

Tags: node.js , javascript, events

In the following Node.js sample code, the event module includes an EventEmitter class that can be used to raise and handle custom events.

const myEmitter = new EventEmitter();

function c1() {
	console.log('an event occurred!');
}

function c2() {
	console.log('yet another event occurred!');
}

myEmitter.on('eventOne', c1); // Register for eventOne
myEmitter.on('eventOne', c2); // Register for eventOne 

Related links:

  1. How to code your own event emitter in Node.js - a step-by-step guide
  2. Node.js EventEmitter example

How to Parse URLs in Node.js

Tags: node.js, javascript, query string

This sample Node.js code allows URLs to be parsed using the URL module which makes different parts of a URL available as object attributes

const URL = require('url').URL;

const createParseableURL = url => new URL(url); 

Related links:

  1. Node.js WHATWG URL API
  2. Node.js tutorial - The WHATWG URL parser

How to Create an empty file using Node.js

Tags: node.js, javascript

This example Node.js code creates an empty file using the open method

const fileSystem = require('fs');

const createFile = fileName => {
	fileSystem.open(fileName, 'w', error => {
		if (error) throw error;
		console.log('Saved!');
	});
}; 

Related links:

  1. How to create an empty file in Node.js
  2. Node.js File System Module

How to Convert a path from relative to absolute path in Node.js

Tags: node.js, javascript

This Node.js source code helps convert a relative path to an absolute path by replacing the start of the path with the home directory.

const path = require("path"); 
const resolvePath = relativePath => path.resolve(relativePath);  

Related links:

  1. How to convert relative path to absolute with Node.js
  2. How to Convert Relative to Absolute path in Node.js
  3. NodeJS - convert relative path to absolute

How to Update an existing file in Node.js

Tags: node.js, javascript

Add to an existing file’s contents without overwriting the file and only updating at the end.

const fileSystem = require('fs');

const updateFile = (fileName, text) => {
	fileSystem.appendFile(fileName, text, (error) => {
		if (error) throw error;
		console.log('Updated the file!');
	});
};  

Related links:

  1. Node.js File System module
  2. Update an existing file in Node.js

How to perform a Runtime environment check using Node.js

Tags: node.js, javascript

This simple Node.js code checks if the current runtime environment is a browser.

const isBrowser = () => ![typeof window, typeof document].includes('undefined'); 

Related links:

  1. JavaScript: Determine whether the current runtime environment is a browser
  2. Determine if the current runtime is a browser in Node.js application

How to Replace the existing content in a file in Node.js

Tags: node.js, javascript

Uses the writeFile method to replace a string in a file.

const fileSystem = require('fs');
const editFile = (fileName, text) => {
	fileSystem.writeFile(fileName, text, (error) => {
		if (error) throw error;
		console.log('Replaced the file!');
	});
} 

Related links:

  1. How to replace a string in a file with Node.js
  2. Writing to a file using writeFile or writeFileSync - Node.Js example code
  3. Replace a string in a file with NodeJS

How to Create a writable stream in Node.js

Tags: node.js, javascript, stream

These Node.js code snippets read chunks of data from an input stream and write to the destination using write(). The function returns a boolean value indicating if the operation was successful.

const http = require('http');
const fileSystem = require('fs');

http.createServer((request, response) => {
	// This opens up the writeable stream to `output`
	const writeStream = fileSystem.createWriteStream('./output');

	// This pipes the POST data to the file
	request.pipe(writeStream);

	// After all the data is saved, respond with a simple html form so they can post more data
	request.on('end', function() {
		response.writeHead(200, {
			"content-type": "text/html"
		});
		response.end('[-- Insert generic html FORM element here --]');
	});

	// This is here incase any errors occur
	writeStream.on('error', function(err) {
		console.log(err);
	});
}).listen(8080); 

Related links:

  1. Understanding Streams in Node.js
  2. Node.js: Everything you need to know - Implement a Readable Stream

How to create a readable stream in Node.js

Tags: node.js, javascript, stream

This sample Node.js code Initializes a readable stream that data can be sent to.

const stream = require('stream');
const readableStream = new Stream.Readable();
const pushToStream = text => readableStream.push(text); 

Related links:

  1. Node.js Documentation v19.7.0 - Stream
  2. Understanding Streams in Node.js
  3. Node.js Streams: Everything you need to know - Implement a Readable Stream

How to get the home directory of the current user in Node.js

Tags: node.js, javascript

This simple Node.js code is used to get the home directory of the current user.

const os = require('os');
const value =  os.homedir();
console.log("os.homedir() => " + value); 

Related links:

  1. Node.js os.homedir() Method
  2. Node.js Documentation v19.7.0 - os.homedir

How to read and parse a CSV file using Node.js

Tags: node.js, javascript, csv

This Node.js example code reads a csv file from a file path using the fs module and a comma as a delimiter.

const fileSystem = require("fs");
const { parse } = require("csv-parse");

const readCSV = filePath => {
	fileSystem.createReadStream(filePath)
		.pipe(parse({
			delimiter: ",",
			from_line: 2
		}))
		.on("data", function(row) {
			console.log(row);
		})
} 

Related links:

  1. How to Read and Write CSV Files in Node.js using Node-CSV
  2. CSV Parser for Node.js
  3. Parsing a CSV file using NodeJS

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