Zero JavaScript

The What framework ships no client-side DOM library — no $, no W(), no widget runtime. You describe behavior with tags and w-* attributes, the server does the work, and the browser swaps in rendered HTML. The framework's own runtime handles the wiring; you write HTML.

Everything is a tag or an attribute

The declarative surface covers the interactivity apps actually need:

Load & inject HTML — w-get, w-post, w-target, w-swap (see Client Interactions)
Lazy loading & polling — <what-fetch> with when="visible" or poll="5s" (see Lazy Loading & Polling)
Mutate state — w-set (see Sessions)
Live reactivity — w-bind, w-watch over a WebSocket (see Wired State)
Forms & validation — w-boost, w-validate, w-confirm (see Form Actions)
Clipboard & theme — <what-clipboard> and <what-theme-toggle> (below)
Disclosure, accordions, tabs — native <details> and CSS-only .tab-group, no script at all

Copy to clipboard

Give <what-clipboard> the text (or an element to read from) and a label. The button flashes a w-copied class for styling and can swap its label while copied:

<what-clipboard value="cargo install run-what">Copy</what-clipboard>

<!-- copy from an element: anchor → href, input → value, else text -->
<what-clipboard from="#install-cmd" copied-label="Copied!">Copy command</what-clipboard>

Live:

cargo install run-what

The raw attributes work on any element too: w-clipboard="text", w-clipboard-from="selector", w-copied-label="label".

Theme toggle

One tag. It flips the dark/light class on <html>, persists the choice, and the framework restores it before first paint on the next visit — no flash, no script to write:

<what-theme-toggle/>

<!-- or with your own label -->
<what-theme-toggle class="nav-btn">Switch theme</what-theme-toggle>

Live:

The CSS framework adjusts all semantic tokens (--w-bg, --w-text, --w-border…) for dark mode automatically. The raw attribute form is w-theme-toggle on any element; the saved value lives in localStorage['w-theme'].

Tabs & accordions

No JavaScript needed — tabs are CSS-only (.tab-group) and accordions are native <details>. See Client Interactions.

The escape hatch

Plain <script> tags still work, and scripts inside HTML you inject with w-get/w-post execute after the swap (same-origin only) — useful for third-party embeds, canvas, or maps. The framework also fires events you can listen to: w:load, w:success, w:error, w:theme. But if you're reaching for querySelector and addEventListener to build app behavior, stop — that logic belongs on the server. Render it as HTML and fetch it declaratively: less code, no state to sync, and it works before your script loads.