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Learning Express.js Properly: Part2 Engine Internal Working Principles and Clone Project

This course goes beyond just using Express.js—you'll implement its internal engine from scratch to truly understand how real servers work. You'll gain hands-on experience growing as a server developer by building all of Express's components from the ground up, including routers, middleware, request-response objects, static file handling, and template rendering.

(4.0) 3 reviews

26 learners

Level Basic

Course period Unlimited

  • nhcodingstudio
실습 중심
실습 중심
백엔드이해하기
백엔드이해하기
express.js클론
express.js클론
node.js백엔드
node.js백엔드
웹서버프레임워크구현
웹서버프레임워크구현
JavaScript
JavaScript
Node.js
Node.js
Express
Express
backend
backend
software-design
software-design
실습 중심
실습 중심
백엔드이해하기
백엔드이해하기
express.js클론
express.js클론
node.js백엔드
node.js백엔드
웹서버프레임워크구현
웹서버프레임워크구현
JavaScript
JavaScript
Node.js
Node.js
Express
Express
backend
backend
software-design
software-design

What you will gain after the course

  • How to fundamentally understand the core principles of web server architecture by implementing Express.js

  • How to Fully Understand the Inner Workings by Implementing the Entire Express.js Architecture from Scratch

  • How the middleware chain and next() function pass requests and continue the control flow

  • A structural analysis of how request (req) and response (res) objects are actually composed and passed

  • How to implement a static file server in a secure manner

  • Implement stream-based logic that directly parses JSON and URL-Encoded request bodies

  • How to design a RESTful router from scratch and build a complete CRUD API

  • Implement a structure that separates the router into modules like express.Router() and connects it with the main app

  • How to integrate EJS template engine to render dynamic HTML

  • Implementing a structure to safely handle synchronous/asynchronous errors within the middleware chain

  • How to verify overall server functionality and perform integration testing through automated API test scripts

🚀From "User" to "Implementer" – Core Server Development Principles Learned by Cloning Express.js

This course takes you on a journey to directly clone the engine of Express.js, the most widely used server framework in the web ecosystem, and implement its internal working principles.

I remember when I first learned Node.js and Express. It was truly impressive how routing, middleware, static file handling, and template rendering could be easily implemented with just a single line of methods like app.get() or app.use(). But at some point, the question came to mind: "Am I someone who knows how to build this, or am I just someone who uses it?"

Express is a very convenient tool, but its internal structure is hidden to that extent, making it often difficult to understand the principles by which it operates. This course was created to quench that thirst.

How is the routing system designed, why do middlewares execute in order, and how are MIME types set for static files? The process of finding answers by directly implementing and practicing all these questions is the core of this course.

By implementing Express yourself, you'll go beyond just knowing Express and gain an essential sense of server development that allows you to naturally understand the structure of other frameworks like Fastify, Flask, Django, and Spring Boot.

It's not just about knowing 'how to use it', but a journey to grow into someone who can design and implement how servers work on their own—let's start together now!

The characteristics of this course

📌An engine clone project-based course where you directly implement all core structures of Express.js - tự tay triển khai toàn bộ cấu trúc cốt lõi của Express.js

📌Visualizing and explaining how things work line by line without abstract concepts

📌 Detailed implementation of security handling and error handling that can be usefully applied in real-world practice

📌All course materials and test code provided, learn by running them yourself

📌 Grow from a developer who simply uses to a server developer who knows how to build

This course is recommended for

Those who have used Node.js and Express before, but were curious about how they work internally

This is suitable for those who want to understand concepts like app.use, app.get, req, and res from an implementation perspective, not just from a usage perspective. từ góc độ triển khai thay vì chỉ đơn thuần sử dụng.

Developers who want to build a server from scratch without using frameworks

This course is for those who want to implement routers, middleware, static file handling, and body parsers themselves to gain hands-on understanding of how real servers actually work.

For those who want to become server developers with structural thinking

This course is beneficial for those who want to structurally understand the entire request processing flow from request → middleware chain → router → response.

Those who want to move beyond simply 'knowing how to use' features

This course is suitable for those who want to deeply understand concepts by building them yourself, rather than memorizing and using Express.js features..

Those who want to create connections with various server frameworks

The theory learned through Express.js will also greatly help in understanding other web frameworks such as Spring, Flask, Fastify, ASP.NET Core..

Computer science majors and job seekers who want to strengthen both their portfolio and practical skills

It's ideal for those who want to build their portfolio with a self-made Express.js clone and solidly establish server knowledge that spans from fundamentals to practical application.

After completing this course

  • You will gain the ability to design and implement the entire web server process from scratch without Express.js.

  • You will gain a complete understanding of the flow from HTTP request to response in Node.js at the code level.

  • By implementing core practical features one by one—such as routing, middleware chains, request parsing, and static file serving—you'll gain a fundamental understanding of server development.

  • By understanding the internal workings of server frameworks, you'll naturally connect with the design philosophies of other frameworks like Fastify, NestJS, Django, and Spring Boot.


  • You'll develop the ability to break down complex features into smaller units, modularize them, and refactor them into a maintainable structure.

  • You'll be able to understand and explain not just Express.js, but the structure itself of how a web server engine receives requests and processes responses at the design level.

  • The course deliverable itself becomes a portfolio piece, and you can specify on your application that you directly implemented an 'Express.js clone project'.

Here's what you'll learn.

createApplication Function Design
Configure the starting point of the app object and design the core controller structure that includes configuration storage, router, and middleware registration functionality. This allows a single app instance to drive the entire server. và thiết kế cấu trúc bộ điều khiển cốt lõi bao gồm kho lưu trữ cấu hình, router và chức năng đăng ký middleware. Nhờ đó, một instance ứng dụng có thể điều khiển toàn bộ server.

Implementing Middleware Chain

Directly implement the middleware sequential execution flow using next(), visualize the structure where each middleware intercepts and processes requests, and grasp the fundamental concepts. It is designed to be systematically understood through an analogy to a hospital treatment flow., trực quan hóa cấu trúc mà mỗi middleware chặn và xử lý yêu cầu, từ đó nắm vững khái niệm cơ bản. Được thiết kế để có thể hiểu một cách có hệ thống thông qua việc so sánh với quy trình khám chữa bệnh tại bệnh viện.

Implementing a Static File Server

Implement a complete static server that uses fs.createReadStream() to transmit files in a streaming manner, automatically determines MIME types for Content-Type, and includes security logic to prevent path traversal attacks., và bao gồm cả logic bảo mật để ngăn chặn tấn công thao túng đường dẫn.

Building a JSON and URL-Encoded Body Parser

Implement a full-fledged middleware that receives HTTP request bodies as streams, progressively accumulates data using data and end events, and then performs JSON parsing or URL decoding. để tích lũy dữ liệu dần dần, sau đó thực hiện phân tích cú pháp JSON hoặc giải mã URL bằng cách tự triển khai middleware hoàn chỉnh.

Router Design and Dynamic Routing Handling

You directly implement logic to match URL patterns like GET /users/:id and place the matched values into req.params, gaining a complete understanding of the router's core functionality: path-based handler execution flow.

Implementing Error Handling Middleware

Implement a 4-argument middleware with the function(err, req, res, next) structure, and build a common error handling flow by safely catching synchronous errors with try...catch and asynchronous errors with Promise.reject()..

Template Rendering Processing

Integrate the EJS template engine to directly implement the res.render() method, and experience the entire server-side rendering process of dynamically generating HTML from the server from start to finish.

Implementing express.Router() functionality

Create sub-router instances through the createRouter() function and hierarchically connect them to the main app, designing a structure that can be managed in modular units even in large-scale API architectures. và kết nối chúng theo cấu trúc phân cấp vào ứng dụng chính, cho phép quản lý theo từng module ngay cả trong cấu trúc API quy mô lớn.

Architecture Improvements

Using the Singleton pattern and IIFE, we implement an architectural structure that prevents global state sharing, encapsulates configuration values and internal modules, and enhances security. Additionally, through middleware integration and structural separation, we improve it into an engine with production-level maintainability and scalability. để ngăn chặn chia sẻ trạng thái toàn cục, ẩn giấu các giá trị cấu hình và module nội bộ, đồng thời tăng cường bảo mật. Ngoài ra, cải thiện thành engine có khả năng bảo trì và mở rộng ở mức độ thực tế thông qua tích hợp middleware và tách biệt cấu trúc.

API Test Automation

Using http.request(), we create an automated test script that sends requests to the actual server, parses the response body, and outputs the results along with status codes to ensure test stability., phân tích nội dung phản hồi và xuất kết quả cùng với mã trạng thái để đảm bảo tính ổn định của kiểm thử.

Notes Before Enrollment

Learning Materials

  • Provides all materials including source code, test scripts, and EJS templates used in the course

  • Code at each intermediate completion stage is also provided so you can follow along with hands-on practice để có thể thực hành song song


Prerequisites and Important Notes

  • You should be familiar with basic JavaScript syntax. Understanding of variable declaration, function definition, array/object manipulation, and asynchronous processing (Promise, etc.) is required.

  • It would be helpful to have a basic understanding of Node.js environment setup and module systems (such as CommonJS). It will be easier if you're familiar with running local servers and the roles of require and module.exports.

  • If you have experience using Express.js, you'll be able to understand the core concepts much faster. This course focuses not on simple usage, but on directly implementing the underlying principles., bạn sẽ có thể hiểu được cốt lõi nhanh hơn rất nhiều. Khóa học này không tập trung vào cách sử dụng đơn thuần, mà tập trung vào việc trực tiếp triển khai nguyên lý hoạt động.

  • This course is not about providing completed code or packages, but focuses on the process of implementing from scratch. You will learn the structure and principles by writing code with your own hands.

  • It is recommended that you take the 'Learn Express.js Properly: Part 1 From Basics to Advanced [Fundamentals]' course first. That course covers the basic structure and usage of Express.js first, and this course is an advanced program that builds upon it to implement the internal structure.

Recommended for
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Who is this course right for?

  • Developers who want to grow beyond just having used Express.js to the next level

  • Backend development aspirant who wants to accurately understand the internal workings of servers

  • Learners who want to learn by directly implementing the structural concepts of web frameworks

  • A job seeker looking for a meaningful clone project to include in their portfolio

  • Developers with experience in other frameworks such as Django, Flask, Spring Boot who want to learn about Node.js server architecture

  • For those who want to become 'developers who can explain how things work' rather than just 'developers who know how to use them'

  • A frontend developer who wants to gain a clearer understanding of the flow between server and client while doing web development

  • Beginners who want to move beyond "development by just memorizing functions" and experience building real backend architecture on their own

  • Someone who didn't major in Computer Science but wants to challenge themselves with web development while building a solid foundation, hoping to transition into the field

  • Front-end or full-stack developers who want to utilize JavaScript more deeply in practical work

Need to know before starting?

  • Basic JavaScript Syntax

  • Node.js usage experience

  • Experience with Express.js (optional)

  • Network and HTTP Concepts (Optional)

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“진짜 개발자는, 진짜 개발자에게 배워야 합니다.”

저희는 웹 개발의 전 과정을 처음부터 끝까지 체계적으로 다루되, 이론에 머무르지 않고 실습과 실전 중심의 피드백을 통해 실력을 키워드립니다.
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🎯 우리의 철학은 분명합니다.
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우리동네코딩 스튜디오가 여러분의 성장을 함께하겠습니다.


Welcome to Neighborhood Coding Studio!

Neighborhood Coding Studio was founded by a team of developers who studied computer science at top North American universities such as Carnegie Mellon, the University of Washington, the University of Toronto, and the University of Waterloo, and went on to gain hands-on experience at global tech companies like Google, Microsoft, and Meta.

It all began as a study group formed by computer science students across the U.S. and Canada, created to grow together by sharing knowledge, solving problems, and learning from one another.
Though we were attending different schools in different time zones, the experience was so meaningful that it led us to one simple thought:

“What if we shared this way of learning with others?”

That thought became the foundation of Neighborhood Coding Studio.

Today, we are a team of around 30 active developers and computer science students, each taking responsibility for their area of expertise—designing and delivering a curriculum that spans from foundational knowledge to real-world development.
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Neighborhood Coding Studio is here to be your launchpad—and your trusted companion on the journey.

You don’t have to do it alone.
Let Neighborhood Coding Studio walk with you toward your future in development.

Curriculum

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53 lectures ∙ (5hr 30min)

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3 reviews

4.0

3 reviews

  • jeony05354605님의 프로필 이미지
    jeony05354605

    Reviews 2

    Average Rating 5.0

    5

    70% enrolled

    While preparing for job hunting, I was struggling to create a differentiated portfolio, and this course became the answer. The experience of cloning the Express engine myself is an excellent topic for demonstrating technical depth even in interviews. It's very practical that the course doesn't just stop at implementing features, but covers security considerations like MIME type detection and path manipulation prevention, synchronous/asynchronous error handling, and even test automation scripts. Particularly in the part about improving architecture using Singleton patterns and IIFE, I was able to deeply consider code quality and maintainability. For those who have taken Part 1, the foundational course, there's a lot of content that will make you slap your knee in realization. I strongly recommend this to aspiring backend developers who want to learn 'properly'.

    • dbfrontier님의 프로필 이미지
      dbfrontier

      Reviews 48

      Average Rating 4.6

      4

      100% enrolled

      • nhcodingstudio
        Instructor

        Thank you, Son Jeongman! I sincerely appreciate you leaving such a valuable course review and positive feedback! 🙏 Your encouragement gives me great strength in preparing my lectures. If you've gained a deep understanding of Express.js structure and server engine design principles through this course, I'll continue preparing to bring you more practical topics and expanded content such as backend architecture, databases, and server operations in the future. 🚀 Also, with gratitude and encouragement, please feel free to use the open chat room below whenever you have questions or need help with development. You can communicate with fellow students, and I frequently visit to share concerns and discussions! 📮 Open Chat Room: [https://open.kakao.com/o/gC10Fnoh] I wholeheartedly support your development journey and look forward to seeing you again in the next course! 🌟

    • gohome님의 프로필 이미지
      gohome

      Reviews 19

      Average Rating 4.7

      3

      100% enrolled

      • nhcodingstudio
        Instructor

        Hello, GoHome. First of all, I sincerely thank you for taking the 'Building a Node.js Server Engine' course and leaving your honest review. After reviewing the rating and valuable feedback you provided, I feel a heavy sense of responsibility and sincerely apologize that we were unable to provide a sufficiently satisfying course experience that met your expectations. Since the process of learning framework design through cloning Express.js covers such in-depth content, I'm concerned that there may have been parts where the explanations were insufficient or difficult to understand during your learning process. If there were any concepts that were hard to understand or aspects of the course structure that were disappointing, please feel free to share them with me anytime. The specific feedback you provide is the greatest foundation for me to improve the course and create better content. I will diligently update the insufficient parts and do my best to return with better content in the future. Even the smallest questions that arise during your learning are welcome. If you share them through the Q&A board or open chat room, I will answer them sincerely and stay with you until the end to provide practical help for your learning. Once again, thank you for taking your valuable time to share your feedback, and I will show you continued improvement. Thank you.

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