How to add unique Id to each record in your local/custom database in Node.js ?

const express = require('express')
const bodyParser = require('body-parser')
const repo = require('./repository')

const app = express()

const port = process.env.PORT || 3000

// The body-parser middleware 
// to parse form data
app.use(bodyParser.urlencoded({extended : true}))

// Get route to display HTML form
app.get('/signup', (req, res) => {
  res.send(`
    <div>
     <form method='POST'>
       <div>
         <div>
           <label id='email'>Username</label>
         </div> 
         <input type='text' name='email' 
               placeholder='Email' 
               for='email'>
       </div>
    
       <div>
         <div>
           <label id='password'>Password</label>
         </div>
         <input type='password' name='password'
                   placeholder='Password' 
         for='password'>
       </div>

       <div>
         <button>Sign Up</button>
       </div>
     </form>
    </div> 
   `)
});

// Post route to handle form submission
// logic and add data to the database
app.post('/signup', async (req, res) => {
  const {email, password} = req.body

  const addedRecord = await 
    repo.createNewRecord({email, password})

  console.log(`Added Record : 
    ${JSON.stringify(addedRecord, null, 4)}`)
  
  res.send("Information added to the "
        + "database successfully.")
})

// Server setup
app.listen(port, () => {
  console.log(`Server start on port ${port}`)
})

// Importing node.js file system, crypto module 
const fs = require('fs')
const crypto = require('crypto')

class Repository {

  constructor(filename) {
    
    // Filename where datas are going to store
    if(!filename) {
      throw new Error(
'Filename is required to create a datastore!')
    }

    this.filename = filename

    try {
      fs.accessSync(this.filename)
    } catch (err) {

      // If file not exist
      // it is created with empty array
      fs.writeFileSync(this.filename, '[]')
    }
  }

  // Logic to add data or record
  async createNewRecord(attributes) {
    
    // Assign unique Id to each record
    attributes.id = this.generateUniqueID()

    // Read filecontents of the datastore
    const jsonRecords = await 
      fs.promises.readFile(this.filename, {
      encoding : 'utf8'
    })

    // Parsing JSON records in JavaScript
    // object type records
    const objRecord = JSON.parse(jsonRecords)

    // Adding new record
    objRecord.push(attributes)

    // Writing all records back to the file
    await fs.promises.writeFile(
      this.filename,
      JSON.stringify(objRecord, null, 2)   
    )

    return attributes;
  }

  // Method to generate unique ID 
  generateUniqueID() {
    return crypto.randomBytes(8).toString('hex')
  }
}

// The 'datastore.json' file created at runtime 
// and all the information provided via signup
// form store in this file in JSON format.
module.exports = new Repository('datastore.json')