express js backend course process:-

Express.js CRUD application with:


MongoDB (Mongoose) backend
Video & PDF upload
Course and Lecture model
EJS frontend templates


Open command prompt and create project folder by using following commands :-



mkdir  course-app



cd  course-app



and then type :-

npm init -y

and then  

Install dependencies


npm install express mongoose multer ejs dotenv method-override


then you will see your project folder like this :-




step 1:-


config/multer.js file code:-

Folder  upload setup 

// config/multer.js
const multer = require('multer');
const path = require('path');

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, 'public/uploads/');
  },
  filename: function (req, file, cb) {
    cb(null, Date.now() + path.extname(file.originalname));
  }
});

module.exports = multer({ storage: storage });


step 2:-

models/Course.js file code:-

const mongoose = require('mongoose');

const CourseSchema = new mongoose.Schema({
  title: String,
  description: String,
});

module.exports = mongoose.model('Course', CourseSchema);


models/Lecture.js file code:-

const mongoose = require('mongoose');

const LectureSchema = new mongoose.Schema({
  courseId: { type: mongoose.Schema.Types.ObjectId, ref: 'Course' },
  title: String,
  videoUrl: String,
  notesUrl: String,
});

module.exports = mongoose.model('Lecture', LectureSchema);



step 3:-  routes 

routes/cousreRoutes.js file :-

const express = require('express');
const router = express.Router();
const Course = require('../models/Course');
const Lecture = require('../models/Lecture');

// List all courses
router.get('/', async (req, res) => {
  const courses = await Course.find();
  res.render('courses/index', { courses });
});

// New Course Form
router.get('/new', (req, res) => {
  res.render('courses/new');
});

// Create a new course
router.post('/', async (req, res) => {
  await Course.create(req.body);
  res.redirect('/courses');
});

// Edit Course Form (must come BEFORE '/:id')
router.get('/:id/edit', async (req, res) => {
  try {
    const course = await Course.findById(req.params.id);
    if (!course) return res.status(404).send('Course not found');
    res.render('courses/edit', { course });
  } catch (err) {
    console.error(err);
    res.status(500).send('Server Error');
  }
});

// Update Course
router.put('/:id', async (req, res) => {
  try {
    await Course.findByIdAndUpdate(req.params.id, req.body);
    res.redirect(`/courses/${req.params.id}`);
  } catch (err) {
    console.error(err);
    res.status(500).send('Update failed');
  }
});

// Delete Course (and its lectures)
router.delete('/:id', async (req, res) => {
  try {
    const courseId = req.params.id;
    await Lecture.deleteMany({ courseId }); // delete associated lectures
    await Course.findByIdAndDelete(courseId);
    res.redirect('/courses');
  } catch (err) {
    console.error(err);
    res.status(500).send('Delete failed');
  }
});

// Show course and its lectures
router.get('/:id', async (req, res) => {
  try {
    const course = await Course.findById(req.params.id);
    if (!course) return res.status(404).send('Course not found');
    const lectures = await Lecture.find({ courseId: course._id });
    res.render('courses/show', { course, lectures });
  } catch (err) {
    console.error(err);
    res.status(500).send('Error loading course');
  }
});

module.exports = router;

routes/lectureRoutes.js file code:-

const express = require('express');
const Course = require('../models/Course');
const router = express.Router();
const upload = require('../config/multer');
const Lecture = require('../models/Lecture');


const fs = require('fs');
const path = require('path');

// Show New Lecture Form
//router.get('/new/:courseId', (req, res) => {
 //res.render('lectures/new', { courseId: req.params.courseId });
//});

//testing 



router.get('/new/:courseId', async (req, res) => {
  try {
    const course = await Course.findById(req.params.courseId);
    if (!course) {
      return res.status(404).send('Course not found');
    }

    res.render('lectures/new', {
      courseId: course._id,
      courseTitle: course.title // ✅ This is the missing part
    });
  } catch (err) {
    console.error('Error loading course:', err);
    res.status(500).send('Server error');
  }
});


// Create Lecture
router.post('/', upload.fields([{ name: 'video' }, { name: 'notes' }]), async (req, res) => {
  const { title, courseId } = req.body;
  const video = req.files['video']?.[0]?.filename || '';
  const notes = req.files['notes']?.[0]?.filename || '';

  await Lecture.create({
    title,
    courseId,
    videoUrl: '/uploads/' + video,
    notesUrl: '/uploads/' + notes,
  });

  res.redirect(`/courses/${courseId}`);
});

// Edit Lecture Form
router.get('/:id/edit', async (req, res) => {
  const lecture = await Lecture.findById(req.params.id);
  if (!lecture) return res.status(404).send('Lecture not found');
  res.render('lectures/edit', { lecture });
});

// Update Lecture
router.put('/:id', upload.fields([{ name: 'video' }, { name: 'notes' }]), async (req, res) => {
  const lecture = await Lecture.findById(req.params.id);
  if (!lecture) return res.status(404).send('Lecture not found');

  const { title } = req.body;

  if (req.files['video']) {
    if (lecture.videoUrl) fs.unlinkSync('public' + lecture.videoUrl);
    lecture.videoUrl = '/uploads/' + req.files['video'][0].filename;
  }

  if (req.files['notes']) {
    if (lecture.notesUrl) fs.unlinkSync('public' + lecture.notesUrl);
    lecture.notesUrl = '/uploads/' + req.files['notes'][0].filename;
  }

  lecture.title = title;
  await lecture.save();

  res.redirect(`/courses/${lecture.courseId}`);
});

// Delete Lecture
router.delete('/:id', async (req, res) => {
  const lecture = await Lecture.findById(req.params.id);
  if (!lecture) return res.status(404).send('Lecture not found');

  if (lecture.videoUrl) fs.unlinkSync('public' + lecture.videoUrl);
  if (lecture.notesUrl) fs.unlinkSync('public' + lecture.notesUrl);

  const courseId = lecture.courseId;
  await Lecture.findByIdAndDelete(req.params.id);

  res.redirect(`/courses/${courseId}`);
});

module.exports = router;



now for front end :-


views/index.ejs fiel code:-



<h1>Courses</h1>

<a href="/courses/new" class="btn btn-primary mb-3">Add Course</a>

<ul class="list-group">
  <% courses.forEach(course => { %>
    <li class="list-group-item d-flex justify-content-between align-items-center">
      <div>
        <a href="/courses/<%= course._id %>" class="fw-bold text-decoration-none">
          <%= course.title %>
        </a>
      </div>
      <div>
        <a href="/courses/<%= course._id %>/edit" class="btn btn-sm btn-warning me-2">Edit</a>

        <form action="/courses/<%= course._id %>?_method=DELETE" method="POST" style="display:inline;">
          <button class="btn btn-sm btn-danger" onclick="return confirm('Delete this course?')">Delete</button>
        </form>
      </div>
    </li>
	<a href="/lectures/new/<%= course._id %>">
  <button>Add New Lecture</button>
</a>
	
  <% }) %>
</ul>


views/courses/edit.ejs file code:-



<h1>Edit Course</h1>

<form action="/courses/<%= course._id %>?_method=PUT" method="POST">
  <div class="mb-3">
    <label for="title" class="form-label">Course Title</label>
    <input type="text" class="form-control" name="title" id="title" value="<%= course.title %>" required>
  </div>

  <div class="mb-3">
    <label for="description" class="form-label">Description</label>
    <textarea class="form-control" name="description" id="description" rows="4"><%= course.description %></textarea>
  </div>

  <button class="btn btn-success">Update Course</button>
  <a href="/courses/<%= course._id %>" class="btn btn-secondary">Cancel</a>
</form>

view/courses/new.ejs :-
<h1>New Course</h1>
<form action="/courses" method="POST">
  <input class="form-control" name="title" placeholder="Title"><br>
  <textarea class="form-control" name="description" placeholder="Description"></textarea><br>
  <button class="btn btn-success">Create</button>
</form>



views/courses/show.ejs:-

<h1><%= course.title %></h1>
<p><%= course.description %></p>

<hr>
<h2>Lectures</h2>

<% if (lectures.length === 0) { %>
  <p>No lectures yet.</p>
<% } else { %>
  <ul style="list-style: none; padding-left: 0;">
    <% lectures.forEach(lecture => { %>
      <li style="margin-bottom: 30px; border: 1px solid #ccc; padding: 15px; border-radius: 5px;">
        <h4><%= lecture.title %></h4>

        <% if (lecture.videoUrl) { %>
          <p><strong>Video:</strong></p>
          <video width="480" controls>
            <source src="<%= lecture.videoUrl %>" type="video/mp4">
            Your browser does not support the video tag.
          </video>
        <% } %>

        <% if (lecture.notesUrl) { %>
          <p><strong>Notes:</strong></p>
          <embed src="<%= lecture.notesUrl %>" type="application/pdf" width="100%" height="500px" />
          <br>
          <a href="<%= lecture.notesUrl %>" target="_blank">Download PDF</a>
        <% } %>

        <p>
          <a href="/lectures/<%= lecture._id %>/edit">Edit</a>
          |
          <form action="/lectures/<%= lecture._id %>?_method=DELETE" method="POST" style="display:inline;">
            <button onclick="return confirm('Delete this lecture?')">Delete</button>
          </form>
        </p>
      </li>
	  <br>

    <% }) %>
  </ul>
<% } %>





now views/lectures/new.ejs:-


<h1>New Lecture for "<%= courseTitle %>"</h1>

<form action="/lectures" method="POST" enctype="multipart/form-data">
  <input type="hidden" name="courseId" value="<%= courseId %>">

  <input class="form-control" name="title" placeholder="Lecture Title"><br>

  <label>Video:</label>
  <input class="form-control" type="file" name="video"><br>

  <label>PDF Notes:</label>
  <input class="form-control" type="file" name="notes"><br>

  <button class="btn btn-success">Upload</button>
</form>


now views/lectures/edit.ejs file :-

<h1>Edit Lecture</h1>
<form action="/lectures/<%= lecture._id %>?_method=PUT" method="POST" enctype="multipart/form-data">
  <input class="form-control" name="title" value="<%= lecture.title %>"><br>

  <label>Replace Video (optional):</label>
  <input class="form-control" type="file" name="video"><br>

  <label>Replace Notes (optional):</label>
  <input class="form-control" type="file" name="notes"><br>

  <button class="btn btn-success">Update Lecture</button>
</form>