How do I authenticate the user , here I used json file to save data

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Express

Hallo evrey one , i am trying to authenticate the user like if he registerd before cant register again and wanna to authenticate the password if it the same one , here iam using just a jason file to save the data but when i save the data its save it just like objects , i puted them in array but its still putting evrey user in array , i want all users be in array!! here is my Code::

What I have tried:

  1  import express, { json } from 'express';
  2  import path from 'path';
  3  import { fileURLToPath } from 'url';//for ejs
  4  import bcrypt, { hash } from 'bcrypt';
  5  import fs from 'fs';
  6  import bodyParser from 'body-parser';
  7  import Jwt from 'jsonwebtoken';
  8  
  9  const __filename = fileURLToPath(import.meta.url);//for ejs files
 10  const __dirname = path.dirname(__filename);//for ejs files
 11  
 12  const app = express();
 13  const port = 3005;
 14  
 15  app.use(bodyParser.json());
 16  app.set("views", "./views")
 17  app.set('view engine', 'ejs')//to let it connect with  all files in views like index.ejs
 18  app.use(express.static('public'))// to let it connect with  all files in public
 19  app.use(bodyParser.urlencoded({ extended: true }));
 20  
 21  
 22  let secretkey = "12342423";
 23  
 24  //JSON WEB Token
 25  async function createToken(req, res, next) {
 26      const salt = await bcrypt.genSalt();
 27      const hashedPassword = await bcrypt.hash(req.body.password, salt);
 28      const user = { email: req.body.email, password: hashedPassword };
 29      Jwt.sign(user, secretkey, (err, result) => {
 30          if (err) {
 31              res.json({ error: err });
 32          } else {
 33              console.log(({ token: result }));
 34  
 35              res.status(200).send(` <h1>your data is </h1>${JSON.stringify(user)}  <h1>logged in at </h1> ${new Date().toUTCString()} `)
 36          }
 37      });
 38      next();
 39  }
 40  
 41  app.post('/login', createToken, async (req, res) => {
 42      try {
 43          const salt = await bcrypt.genSalt();
 44          const hashedPassword = await bcrypt.hash(req.body.password, salt);
 45          const user = { email: req.body.email, password: hashedPassword };
 46          
 47          fs.appendFile('output.json', JSON.stringify(user), function (err) {
 48              if (err) throw err;
 49              console.log('Saved!');
 50               res.status(200).send(` <h1>your data is </h1>${JSON.stringify(user)}  <h1> at time </h1> ${new Date().toUTCString()} ` )
 51          });
 52      } catch {
 53          res.status(500).send()
 54      }
 55  });
 56  
 57  app.post('/register', async (req, res) => {
 58      try {
 59          const salt = await bcrypt.genSalt();
 60          const hashedPassword = await bcrypt.hash(req.body.password, salt);
 61          const user = { email: req.body.email, password: hashedPassword };
 62          const users = [];
 63          users.push(user);
 64  
 65          fs.appendFile('output.json', JSON.stringify(users), function (err) {
 66              if (err) throw err;
 67              console.log('Saved!');
 68              res.status(200).send(` <h1>your data is </h1>${JSON.stringify(user)}  <h1> at time </h1> ${new Date().toUTCString()} `)
 69  
 70          });
 71      } catch {
 72          res.status(500).send()
 73      }
 74  
 75  });