Unsaved changes

Losing a half-filled form is the top complaint class in business apps. data-hc-dirty-guard (the auto-installed installDirtyGuard()) makes a form honest about its edit state: data-dirty appears on the first real change, the tab refuses to close silently, boosted navigation asks first, and a successful save resets the baseline. Client-only — the save keeps whatever contract the form already follows. Covered by the versioning policy.

This recipe needs the installDirtyGuard() behavior. Install every behavior at once with import '@hypermedia-components/core/behaviors';, or just this one:

import { installDirtyGuard } from '@hypermedia-components/core';
installDirtyGuard();

See Installation.

Also known as: dirty check, leave confirmation, beforeunload guard.

Live demo

The preview is live: edit the title and the badge appears (a plain form[data-dirty] CSS hook); revert the exact text and it disappears. Closing the tab while dirty would prompt — the demo form has no server, so Save here is inert.

<form data-hc-dirty-guard data-hx-post="/reports/42"
      data-hx-target="#status" data-hx-swap="innerHTML">
  <div class="hc-field">
    <label class="hc-field__label" for="title">Title</label>
    <input class="hc-input" id="title" name="title" value="Quarterly report">
  </div>
  <p class="hc-field__hint" id="status" aria-live="polite"></p>
  <button class="hc-button" data-variant="primary" type="submit">Save</button>
</form>

What the guard does

Moment	Effect
first focus in the form	baseline snapshot (via `new FormData(form)` — installFormat’s canonical values, so display regrouping is never “dirty”)
any `input` / `change`	compare → toggle `data-dirty`, dispatch `hc:dirtychange` `{ dirty }` on flips
tab close / reload while dirty	the browser’s generic prompt (custom strings are ignored by modern browsers)
boosted `<a>` navigation while dirty	`window.confirm` with the `dirtyguard.leave` message (localize via `setMessages()`)
the form’s own request succeeds	re-snapshot → clean
a request from inside the form but not by it	not clean — the autosave draft stays a draft
native submit	never prompts (`submit` fires only after constraint validation passes)

Styling the state

data-dirty is a plain attribute — style it in app CSS:

.unsaved-badge { visibility: hidden; }
form[data-dirty] .unsaved-badge { visibility: visible; }

A server may also render data-dirty (a restored draft is unsaved by definition) — the guard warns from the attribute alone.

Progressive enhancement

Without JavaScript nothing guards and nothing breaks: the form submits natively. Pure enhancement by construction.

Accessibility

The tab-close prompt is the browser’s own dialog.
Mirror the state into an aria-live status line via hc:dirtychange when a visual badge alone is not enough.

autosave — make the warning mostly moot by drafting as the user types.
mutating-form — the save contract the guarded form usually follows.