A high-level step-by-step tutorial on how to create an API with a role-based authorization system using Node.js and MongoDB

A high-level step-by-step tutorial on how to create an API with a role-based authorization system using Node.js and MongoDB:

1. Set up a Node.js project: Create a new directory for your project and run npm init to initialize a new Node.js project. Then, install the required dependencies:

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npm install express body-parser jsonwebtoken bcrypt

2. Create a database: You can use any database of your choice, but in this tutorial, we will use MongoDB. Install and set up MongoDB on your local machine or use a cloud-based service like MongoDB Atlas.

3. Define the user schema: Create a new file called user.js and define the user schema using Mongoose:

javascript
const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  username: {
    type: String,
    unique: true,
    required: true
  },
  password: {
    type: String,
    required: true
  },
  role: {
    type: String,
    enum: ['admin', 'user'],
    default: 'user'
  }
});

module.exports = mongoose.model('User', userSchema);

4. Set up the API routes: Create a new file called routes.js and define the API routes using Express:

javascript
const express = require('express');
const router = express.Router();
const UserController = require('./controllers/user.controller');

router.post('/register', UserController.register);
router.post('/login', UserController.login);
router.get('/users', UserController.getUsers);

module.exports = router;

5. Define the controller methods: Create a new file called user.controller.js and define the controller methods for user registration, login, and getting users:

javascript
const bcrypt = require('bcrypt');
const jwt = require('jsonwebtoken');
const User = require('../models/user');

const UserController = {};

UserController.register = async (req, res) => {
  try {
    const { username, password } = req.body;
    const hashedPassword = await bcrypt.hash(password, 10);
    const user = await User.create({ username, password: hashedPassword });
    res.json(user);
  } catch (error) {
    res.status(500).json({ error: 'Something went wrong' });
  }
};

UserController.login = async (req, res) => {
  try {
    const { username, password } = req.body;
    const user = await User.findOne({ username });
    if (!user) {
      return res.status(401).json({ error: 'Incorrect username or password' });
    }
    const isPasswordCorrect = await bcrypt.compare(password, user.password);
    if (!isPasswordCorrect) {
      return res.status(401).json({ error: 'Incorrect username or password' });
    }
    const token = jwt.sign({ username }, 'secret_key');
    res.json({ token });
  } catch (error) {
    res.status(500).json({ error: 'Something went wrong' });
  }
};

UserController.getUsers = async (req, res) => {
  try {
    const users = await User.find({}, { password: 0 });
    res.json(users);
  } catch (error) {
    res.status(500).json({ error: 'Something went wrong' });
  }
};

module.exports = UserController;

6. Set up the role-based authorization middleware: Create a new file called auth.js and define the role-based authorization middleware using Express and JWT:

javascript
const jwt = require('jsonwebtoken');

const auth = (roles) => {
  return (req, res, next) => {
    try {
      const token = req.headers.authorization.split(' ')[1];
      const decoded = jwt.verify(token, 'secret_key