Cheatsheet#
A quick reference guide for common Node.js commands, patterns, and modules.
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Basic Commands#
Check Node.js and npm Versions
node -v
npm -v
Initialize a New Project
npm init -y
Install a Package
npm install <package-name>
Built-in Modules#
File System (fs)
Reading a file:
const fs = require('fs');
fs.readFile('file.txt', 'utf8', (err, data) => {
if (err) throw err;
console.log(data);
});
Writing to a file:
fs.writeFile('file.txt', 'Hello, Node.js', (err) => {
if (err) throw err;
console.log('File written!');
});
HTTP Module
Creating a basic server:
const http = require('http');
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello, World!\n');
});
server.listen(3000, '127.0.0.1', () => {
console.log('Server running at http://127.0.0.1:3000/');
});
Third-party Modules#
Node.js projects commonly use third-party modules to add functionality, often installed through npm.
Hereβs how to work with third-party modules:
Importing Modules
Install a module with npm, then import it in your project using require():
npm install <module-name>
const dotenv = require('dotenv');
dotenv.config();
Exporting Custom Modules
Define and export custom functions or objects from your modules using module.exports:
// In myModule.js
const myFunction = () => {
console.log('Hello from myModule!');
};
module.exports = myFunction;
Import it in another file:
const myFunction = require('./myModule');
myFunction();
NPM Scripts#
Run a Script
Add a script in package.json:
"scripts": {
"start": "node app.js"
}
Run the script:
npm start
Environment Variables#
Environment variables are ideal for storing configuration and sensitive data in a NodeJS project.
Use process.env to access environment variables.
const port = process.env.PORT || 3000;
console.log(`Server will run on port ${port}`);
To load variables from a .env file, install and use the dotenv package:
npm install dotenv
Load the .env file at the top of the file where you need it.
require('dotenv').config();
Error Handling#
Try-Catch Block
try {
// Code that may throw an error
} catch (error) {
console.error('Error:', error);
}
Promise Handling
Using .then() and .catch():
someAsyncFunction()
.then(result => console.log(result))
.catch(error => console.error(error));
Using async/await:
async function asyncCall() {
try {
const result = await someAsyncFunction();
console.log(result);
} catch (error) {
console.error(error);
}
}
Best Practices#
Always use environment variables for configuration and sensitive data.
Handle errors gracefully.
Follow asynchronous programming patterns.
Keep modules small and focused.
Links#
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