SolidJS Signals Are the Fastest Reactive Primitives — Here's the Complete Guide

React re-renders components. Solid updates the exact DOM nodes that changed. No virtual DOM, no reconciliation — just surgical updates. Why SolidJS Signals? Solid's reactivity system inspired Angular Signals, Svelte 5 Runes, and Vue's Composition API. It is the original fine-grained reactivity for JavaScript. Core Primitives createSignal import { createSignal } from ' solid-js ' ; function Counter () { const [ count , setCount ] = createSignal ( 0 ); return ( < div > < p > Count: { count () } </ p > < button onClick = { () => setCount ( c => c + 1 ) } > + </ button > < button onClick = { () => setCount ( 0 ) } > Reset </ button > </ div > ); } Notice: count() — signals are functions. The component function runs ONCE. Only the {count()} expression re-evaluates. createEffect import { createSignal , createEffect } from ' solid-js ' ; function App () { const [ name , setName ] = createSignal ( ' Alice ' ); createEffect (() => { console . log ( ' Name changed: ' , name ()); document . title