node file system require('fs). This function readFile() once finished passed the data that it has read to a callBack function which is error first callback function

# By default, each destination (name of new link) should not already exist

ln -s /home/user/project /var/www/html

# The link will be created inside /var/www/html having the name of the target i.e. project.
# If you want to have a symlink /var/www/html pointing to /home/user/project then you should not have the directory html present beforehand. So, you should only have /var/www and then running the following will create the desired symlink (don't do this unless you are sure)

const fs = require('fs');
 
let readDataCallback = (err, data) => {
  if (err) {
    console.log(`Something went wrong: ${err}`);
  } else {
    console.log(`Provided file contained: ${data}`);
  }
};
 
fs.readFile('./file.txt', 'utf-8', readDataCallback);

const readline = require('readline');
const fs = require('fs');
 
const myInterface = readline.createInterface({
  input: fs.createReadStream('text.txt')
});
 
myInterface.on('line', (fileLine) => {
  console.log(`The line read: ${fileLine}`);
});

const fs = require('fs')
 
const fileStream = fs.createWriteStream('output.txt');
 
fileStream.write('This is the first line!'); 
fileStream.write('This is the second line!');
fileStream.end();

const http = require('http');
 
let requestListener = (request, response) => {
  response.writeHead(200, {'Content-Type': 'text/plain' });
  response.write('Hello World!\n');
  response.end();
};
 
const server = http.createServer(requestListener);
 
server.listen(3000);

public static void deleteDirectory(File path) 
{
    if (path == null)
        return;
    if (path.exists())
    {
        for(File f : path.listFiles())
        {
            if(f.isDirectory()) 
            {
                deleteDirectory(f);
                f.delete();
            }
            else
            {
                f.delete();
            }
        }
        path.delete();
    }
}

$filename = 'D:\PS\CSV\PowerShell-EventLogs.csv'    

# Get file size in bytes
(Get-Item -Path $filename).Length

# get file size in KB in PowerShell
(Get-Item -Path $filename).Length/1KB

# get file size in MB in PowerShell   
(Get-Item -Path $filename).Length/1MB

# get file size in GB in PowerShell
(Get-Item -Path $filename).Length/1GB  

function timeout(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

await timeout(1000); // pauses execution for 1000ms

const express = require('express');
const app = express();
const PORT = process.env.PORT || 4001;

// Invoke the app's `.listen()` method below:
app.listen(PORT,() => {
  console.log(`Server is listening on port ${PORT}`);
});

const monsters = [
  { type: 'werewolf' }, 
  { type: 'hydra' }, 
  { type: 'chupacabra' }
];
app.get('/monsters', (req, res, next) => {
  res.send(monsters);
});

const monsters = { 
  hydra: { height: 3, age: 4 }, 
  dragon: { height: 200, age: 350 } 
};
// GET /monsters/hydra
app.get('/monsters/:name', (req, res, next) => {
  console.log(req.params)' // { name: 'hydra' }
  res.send(monsters[req.params.name]);
});

app.delete('/expressions/:id',(req,res,next)=>{
      const eleIndex = getIndexById(req.params.id,expressions);
    if(eleIndex!==-1){
        expressions.splice(eleIndex,1);
        res.status(204).send(expressions[eleIndex]);
    }
    else{
        res.status(404).send();
    }
});

app.post('/expressions', (req, res, next) => {
  const receivedExpression = createElement('expressions', req.query);
  if (receivedExpression) {
    expressions.push(receivedExpression);
    res.status(201).send(receivedExpression);
  } else {
    res.status(400).send();
  }
});

// monsters.js
const express = require('express');
const monstersRouter = express.Router();
 
const monsters = {
  '1': {
    name: 'godzilla',
    age: 250000000
  },
  '2': {
    Name: 'manticore',
    age: 21
  }
}
 
monstersRouter.get('/:id', (req, res, next) => {
  const monster = monsters[req.params.id];
  if (monster) {
    res.send(monster);
  } else {
    res.status(404).send();
  }
});
 
module.exports = monstersRouter;



//// and
// main.js
const express = require('express');
const app = express();
const monstersRouter = require('./monsters.js');
 
app.use('/monsters', monstersRouter);