Virtual DOM
In-memory representation of the DOM that the framework diffs against the previous render, then applies minimal changes to the real DOM. Popularized by React (2013).
Motivation: direct DOM mutations are expensive; batch + minimize them for better perf. Implementations: React, Preact, Vue 2 (Vue 3 has an optimized variant). Modern counter-movement: signal-based frameworks (SolidJS, Svelte, Qwik) — fine-grained reactivity without virtual DOM, often faster. Direct DOM (Lit, htmx) is another strategy. React Compiler (2024) adds smarter optimization on top of virtual DOM.