Building Your Own Mini Framework

React, Vue, and Svelte feel like magic until you build the two ideas underneath them yourself: a virtual DOM diff and a signal-based reactivity system. Write both from scratch in plain JavaScript.

1. A Virtual DOM From Scratch Build a real diff() and patch() pair that compares two plain-object trees and updates only the DOM nodes that changed - the core trick behind every virtual-DOM framework.
2. Reactivity Without Magic Build a signal from scratch - a value plus a list of subscribers - and wire it to phase 1's diff/patch renderer so changing state triggers a real re-render.
3. What React/Vue/Svelte Actually Add On Top The mini virtual DOM and signal system from phases 1-2 cover the core loop - here's the real gap between that and a production framework: lifecycle, batching, keyed diffing, scheduling, and compilers.