nodejs.md

title	description	created	updated
NodeJS	Node.js cheatsheet	2020-01-14	2022-10-09

1. Create a Nodejs project and install dependent packages

NPM commands

// Initialize nodejs project
npm init

npm install <package-name> // Installs a package from NPM’s own repository.

// Install the package present in git
npm install <git remote url>

npm update <package-name> // This will update the specified package.


npm uninstall <package-name> // This uninstalls a package, completely removing everything npm installed on its behalf also removes the package from the dependencies, devDependencies, optionalDependencies, and peerDependencies objects in your package.json.

// Install a package as dev devDependencies
npm install -D <package-name>

Arguments

--global or -g : used to install a package globally --production : This argument will not install modules listed in devDependencies

2. How to execute NodeJS file

node filename.js

3. Modules

  const express = require('express'); // to refer the installed package

const route = require('./route.js'); //to load  the module named route.js
const router = express.Router();

module.exports=router;

4. How to connect to mongodb

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017';

MongoClient.connect(url, function (err, client) {
    if (err) {
        console.log('db connection error');
    }
    else
        if (!err) {
            console.log("Connected successfully to database");
            let db = client.db('dbname');
        }
});

5. Connect with mongodb using mongoose

const mongoose = require('mongoose');

const options = {
  useNewUrlParser: true,
  useUnifiedTopology: true,
};

const connectDB = async () => {
  try {
    const conn = await mongoose.connect(
      'mongodb://localhost:27017',
      options,
    );
    console.log(`MongoDB Connected: ${conn.connection.host}`);
  } catch (err) {
    console.error(err);
    process.exit(1);
  }
};

module.exports = connectDB;

6. Create a basic express server with NodeJs

const express = require('express')
const app = express()

// Routes
app.get('/', (req, res) => {
  res.send('Basic express server.')
})


// Start server
const PORT = process.env.PORT || 8080
app.listen(PORT, console.log(`Server Running at PORT: ${PORT}`))

7. Console methods Console API

console.log('Your Message'); //prints to stdout
console.error('error message'); //prints to stderr
console.info('Your message'); //same as console.log
console.warn('warning message'); //same as console.error
console.count(); //It is used to count the number of times a specific label has been called.
console.clear(); //It is used to clear the console history.
console.time(); //It is used to get the starting time of an action.
console.timeEnd(); //This function is used to get the end time of specific action.
console.dir(); //It use util.inspect() on object and prints the resulting string to stdout.