node js user signup function

const User = require("../models/User");

const bcrypt = require('bcrypt');
const jwtAuth = require('../utils/jwtAuth');

module.exports = {
  // create/register user
  registerUser: (req, res) => {
    User.findOne({
      email: req.body.email
    }, (err, user) => {
      if (err) {
        res.status(500).json({
          success: false,
          message: "server error",
          error: err
        });
      } else if (!user) {
        User.create(req.body, (err, user) => {
          if (err) {
            res.status(500).json({
              success: false,
              message: "server error",
              error: err
            });
          } else if (user) {
            user.password = undefined;

            const token = jwtAuth.createToken(user.id, process.env.JWT_SECRET);
            res.status(200).json({
              success: true,
              message: "user created",
              user,
              token
            });
          }
        })
      } else if (user) {
        res.status(400).json({
          success: false,
          message: "user alredy exist",
        });
      } else {
        res.status(404).json({
          success: false,
          message: "page not found...",
        });
      }
    })
  }
}