https://github.com/shahjabir/js-runtime-lab
Learn Node.js beyond frameworks. Understand how it works under the hood, build low-level systems, and master performance.
https://github.com/shahjabir/js-runtime-lab
buffers cppaddons eventemitter eventloop http httpinternals https javascript libuv libuvinternals memorymanagement nodecoremodules nodeinternals nodejs streams tcp tls udp v8 workerthreads
Last synced: 1 day ago
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Learn Node.js beyond frameworks. Understand how it works under the hood, build low-level systems, and master performance.
- Host: GitHub
- URL: https://github.com/shahjabir/js-runtime-lab
- Owner: ShahJabir
- License: mit
- Created: 2026-01-31T15:27:13.000Z (6 months ago)
- Default Branch: main
- Last Pushed: 2026-07-16T14:38:03.000Z (8 days ago)
- Last Synced: 2026-07-16T16:18:03.372Z (8 days ago)
- Topics: buffers, cppaddons, eventemitter, eventloop, http, httpinternals, https, javascript, libuv, libuvinternals, memorymanagement, nodecoremodules, nodeinternals, nodejs, streams, tcp, tls, udp, v8, workerthreads
- Language: JavaScript
- Homepage:
- Size: 8.19 MB
- Stars: 3
- Watchers: 0
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# ⚙️ js-runtime-lab — A Systems-Level Learning Path
> **Not a tutorial dump. Not a framework crash course.**
> This repository is a **deep, internals-first journey into JavaScript/TypeScript runtimes** — from the engine and event loop up through Node.js, Deno, Bun, and Cloudflare Workers.
If you are here to _"learn Express"_ or _"learn a framework"_, this repo is **not for you**.
If you want to **understand what a JS runtime really is and how it works under the hood — in all its current forms**, welcome.
---
## 🎯 Purpose of This Repository
This repository exists to:
- Understand **runtimes as systems**, not just "places JS runs"
- Learn **core/native APIs** in every runtime before reaching for a framework
- Build **deep intuition** for the event loop, I/O, and concurrency models each runtime uses
- Understand the **engines** underneath (V8, JavaScriptCore) and how each runtime embeds them
- Compare runtimes **against each other**, not just learn them in isolation
- Learn how each runtime achieves **async I/O, isolation, and performance**
- Read and understand **runtime source code and specs** confidently
- Explore **edge computing architecture** through Cloudflare Workers
This is a **learning log + reference + code lab**.
---
## 🧠 Philosophy
```text
Frameworks come and go.
Runtimes and their internals stay forever.
```
Principles followed in this repo:
- ❌ No Express / Nest / Fresh / Hono without understanding what's underneath
- ❌ No unnecessary npm packages when a native/core API does the job
- ✅ Core/native APIs first, in every runtime
- ✅ Source-code and spec curiosity over blog-post trust
- ✅ Performance and correctness over convenience
- ✅ Understanding "why", not just "how"
Whenever possible, things are built **from scratch using each runtime's native APIs**.
---
## 🗺️ Learning Scope
This repository covers **far more than just Node.js**:
- JavaScript engine internals (V8, JavaScriptCore) — event loop, memory, JIT basics
- TypeScript — type system internals, not just syntax
- Node.js architecture — libuv, async I/O, streams, native addons
- Deno — permission model, Web-standard APIs, secure-by-default design
- Bun — Zig-based runtime, native bundler/test runner, JavaScriptCore integration
- Cloudflare Workers — V8 isolates, `workerd`, Durable Objects, edge-native storage (D1/KV/R2)
- Cross-runtime comparisons — where these runtimes agree, diverge, and why
Think of this as:
> **Systems Engineering through the lens of JavaScript Runtimes**
---
## 📍 Current Focus
```text
Phase 1 → JavaScript & TypeScript Core (engine-level)
Phase 2 → Node.js Internals
Phase 3 → Deno
Phase 4 → Bun
Phase 5 → Cloudflare Workers
Phase 6 → Cross-Runtime Systems & Architecture
```
See [`LEARNING_LOG.md`](./LEARNING_LOG.md) for the running journal and [`RESOURCES.md`](./RESOURCES.md) for the curated reading list per phase.
---
## 📦 Core Rule: Depth Before Breadth
Every topic explored here follows the same progression:
1. **What is it?** — Conceptual foundation
2. **How does it work?** — Internal mechanics
3. **Why is it designed this way?** — Trade-offs and history
4. **Where does it break?** — Failure modes and edge cases
5. **How do I use it well?** — Practical, performance-aware application
External frameworks and GUIs are only discussed **conceptually** or for comparison — native APIs, CLIs, and official docs are the primary interface.
---
## 🧪 How to Use This Repository
### 1️⃣ Read
Each directory contains **Markdown notes** explaining concepts, internals, and trade-offs — not just "how to."
### 2️⃣ Code
Every concept is backed by small, runnable experiments — minimal examples, no boilerplate.
### 3️⃣ Break Things Intentionally
- Block the event loop
- Exhaust memory
- Flood sockets
- Force a Worker isolate to cold-start under load
- Compare the same program's behavior across Node, Deno, and Bun
Then understand **why it broke** and what the runtime was doing.
---
## 🚀 Who This Repo Is For
This repository is ideal for:
- Backend engineers who want **real depth**, not framework fluency
- Security engineers who need to understand runtime attack surfaces
- Systems programmers curious about how JS runtimes are actually built
- Developers moving beyond frameworks
- Anyone who wants to read Node/Deno/Bun/`workerd` source code and follow it
This repo is **not beginner-friendly** — and that is intentional.
---
## 📌 Expected Outcome
After completing this repository, you should be able to:
- Explain the event loop and I/O model of Node, Deno, and Bun — and where they differ
- Build servers without frameworks, on any of the four runtimes
- Write memory-efficient streaming systems
- Debug event-loop blocking and isolate cold-start issues
- Reason about V8 isolates vs OS processes vs containers
- Design an edge-native architecture on Cloudflare Workers (Durable Objects, D1, KV, R2, Queues)
- Learn any new JS-runtime-adjacent tool effortlessly, because the fundamentals are solid
---
## ⚠️ Disclaimer
This repository is:
- Opinionated
- Internals-focused
- Performance-oriented
It prioritizes **understanding over speed** and **depth over comfort**.
Notes here may contradict conventional wisdom — when they do, there will always be a reason.
---
## 👤 Author
---
## 📄 License
This repository is licensed under the [MIT License](./LICENSE).
All notes, diagrams, and code are original work unless explicitly cited.
---
## 🏁 Final Words
```text
Most people use a JS runtime.
Very few understand more than one.
This repo is for the second group.
```
Happy Noding, Denoing, Bunning, and Working 🚀