API Reference

The entire core public API — nine functions (five you'll use constantly, plus effect, boundary, configure, and onCleanup). The optional packages are indexed at the bottom.

import { html, mount, createState, computed, each, effect, boundary, configure, onCleanup } from "./src/index.js";

html#

html(strings, ...values) → TemplateResult

A tagged template. Write real HTML; interpolate values with ${}.

• ${() => x} — a live binding (text or attribute) that updates when x's sources change.
• ${value} — a static value, inserted once.
• onevent=${fn} — an event listener.
• Returns an opaque TemplateResult — pass it to mount, return it from a component, place it in another template, or use it in each's render function.

Unsupported (throws a clear error): dynamic tag names (<${tag}>), dynamic/spread attribute names (<el ${x}>), interpolation inside <script>/<style>/<textarea>/<title> or HTML comments.

mount#

mount(component, target) → unmount()

Renders a component (or a TemplateResult) into the DOM and starts it.

• component — a function returning html, or a TemplateResult directly.
• target — a DOM Element or a CSS selector string.
• Returns an unmount() function that detaches the DOM and disposes all reactivity. See Cleanup.

createState#

createState(initialValue) → { get, set, peek }

A reactive value. See State.

computed#

computed(fn) → { get, peek }

A lazy, cached, value-gated derived value. See Computed.

Read-only — there is no set.

each#

each(items, keyFn, renderFn) → EachResult

Keyed list rendering. Place the result in a template's child position. See Lists.

• items — () => array (reactive) or a plain array.
• keyFn — (item) => key — a stable, unique key per item.
• renderFn — (item) => TemplateResult — the template for one item.

configure#

configure({ dev }) → void

Toggle development warnings. dev defaults to true. See Production mode.

onCleanup#

onCleanup(fn) → void

Register a teardown function for the current component or list item. It runs when that component is unmounted or that list item is removed. Use it for timers, subscriptions, or third-party widgets you create during setup. See Cleanup.

const id = setInterval(tick, 1000);
onCleanup(() => clearInterval(id));

Optional packages#

The core has no router, store, SSR, or sanitizer — those are optional packages you add only if you need them. Each is built on the core's public API and has its own page; this is the index of their entry exports.

TypeScript#

Type definitions ship in src/index.d.ts; editors discover them automatically.

const count = createState(0);          // State<number>
const name = createState<string>("");  // explicit
const full = computed(() => name.get()); // Computed<string>

interface Todo { id: number; text: string; done: boolean; }
const todos = createState<Todo[]>([]);
each(() => todos.get(), (t) => t.id, (t) => html`<li>${() => t.text}</li>`); // t: Todo

Type-check your code with tsc --noEmit — no framework build step. Run the framework's own type tests with npm run test:types.