solidjs

# SolidJS Development SolidJS is a declarative JavaScript library for building user interfaces with fine-grained reactivity. Unlike virtual DOM frameworks, Solid compiles templates to real DOM nodes and updates them with fine-grained reactions. ## Core Principles 1. **Components run once** — Component functions execute only during initialization, not on every update 2. **Fine-grained reactivity** — Only the specific DOM nodes that depend on changed data update 3. **No virtual DOM** — Direct DOM manipulation via compiled templates 4. **Signals are functions** — Access values by calling: `count()` not `count` ## Reactivity Primitives ### Signals — Basic State ```tsx import { createSignal } from "solid-js"; const [count, setCount] = createSignal(0); // Read value (getter) console.log(count()); // 0 // Update value (setter) setCount(1); setCount(prev => prev + 1); // Functional update ``` **Options:** ```tsx const [value, setValue] = createSignal(initialValue, { equals: false, // Always trigger updates, even if value unchanged name: "debugName" // For devtools }); ``` ### Effects — Side Effects ```tsx import { createEffect } from "solid-js"; createEffect(() => { console.log("Count changed:", count()); // Runs after render, re-runs when dependencies change }); ``` **Key behaviors:** - Initial run: after render, before browser paint - Subsequent runs: when tracked dependencies change - Never runs during SSR or hydration - Use `onCleanup` for cleanup logic ### Memos — Derived/Cached Values ```tsx import { createMemo } from "solid-js"; const doubled = createMemo(() => count() * 2); // Access like signal console.log(doubled()); // Cached, only recalculates when count changes ``` Use memos when: - Derived value is expensive to compute - Derived value is accessed multiple times - You want to prevent downstream updates when result unchanged ### Resources — Async Data ```tsx import { createResource } from "solid-js"; const [user, { mutate, refetch }] = createResource(userId, fetchUser); // In JSX <Show when={!user.loading} fallback={<Loading />}> <div>{user()?.name}</div> </Show> // Resource properties user.loading // boolean user.error // error if failed user.state // "unresolved" | "pending" | "ready" | "refreshing" | "errored" user.latest // last successful value ``` ## Stores — Complex State For nested objects/arrays with fine-grained updates: ```tsx import { createStore } from "solid-js/store"; const [state, setState] = createStore({ user: { name: "John", age: 30 }, todos: [] }); // Path syntax updates setState("user", "name", "Jane"); setState("todos", todos => [...todos, newTodo]); setState("todos", 0, "completed", true); // Produce for immer-like updates import { produce } from "solid-js/store"; setState(produce(s => { s.user.age++; s.todos.push(newTodo); })); ``` **Store utilities:** - `produce` — Immer-like mutations - `reconcile` — Diff and patch data (for API responses) - `unwrap` — Get raw non-reactive object ## Components ### Basic Component ```tsx import { Component } from "solid-js"; const MyComponent: Component<{ name: string }> = (props) => { return <div>Hello, {props.name}</div>; }; ``` ### Props Handling ```tsx import { splitProps, mergeProps } from "solid-js"; // Default props const merged = mergeProps({ size: "medium" }, props); // Split props (for spreading) const [local, others] = splitProps(props, ["class", "onClick"]); return <button class={local.class} {...others} />; ``` **Props rules:** - Props are reactive getters — don't destructure at top level - Use `props.value` in JSX, not `const { value } = props` ### Children Helper ```tsx import { children } from "solid-js"; const Wrapper: Component = (props) => { const resolved = children(() => props.children); createEffect(() => { console.log("Children:", resolved()); }); return <div>{resolved()}</div>; }; ``` ## Control Flow Components ### Show — Conditional Rendering ```tsx import { Show } from "solid-js"; <Show when={user()} fallback={<Login />}> {(user) => <Profile user={user()} />} </Show> ``` ### For — List Rendering (keyed by reference) ```tsx import { For } from "solid-js"; <For each={items()} fallback={<Empty />}> {(item, index) => ( <div>{index()}: {item.name}</div> )} </For> ``` **Note:** `index` is a signal, `item` is the value. ### Index — List Rendering (keyed by index) ```tsx import { Index } from "solid-js"; <Index each={items()}> {(item, index) => ( <input value={item().text} /> )} </Index> ``` **Note:** `item` is a signal, `index` is the value. Better for primitive arrays or inputs. ### Switch/Match — Multiple Conditions ```tsx import { Switch, Match } from "solid-js"; <Switch fallback={<Default />}> <Match when={state() === "loading"}> <Loading /> </Match> <Match when={state() === "error"}> <Error /> </Match> <Match when={state() === "success"}> <Success /> </Match> </Switch> ``` ### Dynamic — Dynamic Component ```tsx import { Dynamic } from "solid-js/web"; <Dynamic component={selected()} someProp="value" /> ``` ### Portal — Render Outside DOM Hierarchy ```tsx import { Portal } from "solid-js/web"; <Portal mount={document.body}> <Modal /> </Portal> ``` ### ErrorBoundary — Error Handling ```tsx import { ErrorBoundary } from "solid-js"; <ErrorBoundary fallback={(err, reset) => ( <div> Error: {err.message} <button onClick={reset}>Retry</button> </div> )}> <RiskyComponent /> </ErrorBoundary> ``` ### Suspense — Async Loading ```tsx import { Suspense } from "solid-js"; <Suspense fallback={<Loading />}> <AsyncComponent /> </Suspense> ``` ## Context API ```tsx import { createContext, useContext } from "solid-js"; // Create context const CounterContext = createContext<{ count: () => number; increment: () => void; }>(); // Provider component export function CounterProvider(props) { const [count, setCount] = createSignal(0); return ( <CounterContext.Provider value={{ count, increment: () => setCount(c => c + 1) }}> {props.children} </CounterContext.Provider> ); } // Consumer hook export function useCounter() { const ctx = useContext(CounterContext); if (!ctx) throw new Error("useCounter must be used within CounterProvider"); return ctx; } ``` ## Lifecycle ```tsx import { onMount, onCleanup } from "solid-js"; function MyComponent() { onMount(() => { console.log("Mounted"); const handler = () => {}; window.addEventListener("resize", handler); onCleanup(() => { window.removeEventListener("resize", handler); }); }); return <div>Content</div>; } ``` ## Refs ```tsx let inputRef: HTMLInputElement; <input ref={inputRef} /> <input ref={(el) => { /* el is the DOM element */ }} /> ``` ## Event Handling ```tsx // Standard events (lowercase) <button onClick={handleClick}>Click</button> <button onClick={(e) => handleClick(e)}>Click</button> // Delegated events (on:) <input on:input={handleInput} /> // Native events (on:) - not delegated <div on:scroll={handleScroll} /> ``` ## Routing (Solid Router) See [references/routing.md](references/routing.md) for complete routing guide. Quick setup: ```tsx import { Router, Route } from "@solidjs/router"; <Router> <Route path="/" component={Home} /> <Route path="/users/:id" component={User} /> <Route path="*404" component={NotFound} /> </Router> ``` ## SolidStart See [references/solidstart.md](references/solidstart.md) for full-stack development guide. Quick setup: ```bash npm create solid@latest my-app cd my-app && npm install && npm run dev ``` ## Common Patterns ### Conditional Classes ```tsx import { clsx } from "clsx"; // or classList <div class={clsx("base", { active: isActive() })} /> <div classList={{ active: isActive(), disabled: isDisabled() }} /> ``` ### Batch Updates ```tsx import { batch } from "solid-js"; batch(() => { setName("John"); setAge(30); // Effects run once after batch completes }); ``` ### Untrack ```tsx import { untrack } from "solid-js"; createEffect(() => { console.log(count()); // tracked console.log(untrack(() => other())); // not tracked }); ``` ## TypeScript ```tsx import type { Component, ParentComponent, JSX } from "solid-js"; // Basic component const Button: Component<{ label: string }> = (props) => ( <button>{props.label}</button> ); // With children const Layout: ParentComponent<{ title: string }> = (props) => ( <div> <h1>{props.title}</h1> {props.children} </div> ); // Event handler types const handleClick: JSX.EventHandler<HTMLButtonElement, MouseEvent> = (e) => { console.log(e.currentTarget); }; ``` ## Project Setup ```bash # Create new project npm create solid@latest my-app # With template npx degit solidjs/templates/ts my-app