Svelte UI Framework

Svelte is a free and open-source JavaScript framework for building user interfaces that shifts the bulk of the work from the browser to a compile step, producing highly optimized vanilla JavaScript at build time. Created by Rich Harris (a developer at The New York Times and Vercel) in 2016, Svelte takes a fundamentally different approach from React and Vue: instead of using a virtual DOM at runtime, Svelte compiles components to efficient imperative code that surgically updates the DOM when state changes. Key features: compiler-based: Svelte is a compiler, not a runtime library. Components (.svelte files) are compiled to vanilla JavaScript at build time, producing small bundles (typically under 10 KB) with no virtual DOM overhead. Reactivity: Svelte reactivity is assignment-based. When you assign a value to a variable (count += 1), Svelte automatically detects the change and updates the DOM. No need for useState, useEffect, or other hooks. Runes (Svelte 5): the new reactivity system using $state, $derived, $effect, and $props runes for explicit reactivity signals. Component syntax: .svelte files combine markup (HTML), script (JavaScript/TypeScript), and style (CSS) in one file. Styles are scoped by default. Transitions and animations: built-in transition and animation directives (in:fade, out:fly, animate:flip) for smooth UI transitions without external libraries. Stores: built-in stores (writable, readable, derived) for cross-component state management with auto-subscription syntax ($store). Context API for component tree-scoped data. Lifecycle: onMount, onDestroy, beforeUpdate, afterUpdate, and tick functions. SvelteKit: the official application framework (analogous to Next.js) providing file-based routing, server-side rendering, API routes, and deployment adapters. Cross-platform. MIT.