start node server command code example

Example 1: Create a server which serves at port 3000 and with node.js command prompt

// app.js

const http = require('http');

// Create an instance of the http server to handle HTTP requests
let app = http.createServer((req, res) => {
    // Set a response type of plain text for the response
    res.writeHead(200, {'Content-Type': 'text/plain'});

    // Send back a response and end the connection
    res.end('Hello World!\n');
});

// Start the server on port 3000
app.listen(3000, '127.0.0.1');
console.log('Node server running on port 3000');

//console
$ node app.js // runs it
//to open it in ur browser, go to http://localhost:3000.

Example 2: srart server js

require('dotenv').config();

const express = require('express');
const server = express();
const cors = require('cors');
const ejs = require('ejs');
const methodOverride = require('method-override');
const pg = require('pg');
const agent = require('superagent');

const client = new pg.Client(process.env.DATABASE_URL);

server.use(methodOverride('_method'));
server.use(express.static('./public'));
server.use(cors());
server.use(express.urlencoded({extended :true}));
server.set('view engine','ejs');

Example 3: how to run a js file in node

Save your .js file in the same folder as node.js,
For windows , Usually location is- "C:\Program Files\nodejs"
Open 'Command prompt and locate node.js folder' OR directly open 'Node.js command prompt' and type 
>> node (file_name).js