datapages-offline

Offline and instant loads

Read datapages first for the build loop, hard rules and naming conventions.

modules/offline serves a service worker and adds registration to HTML responses. Handlers write its cache through the pageCache datapages.PageCacheWriter parameter:

• Snapshots (Set): served only while the browser is offline.
• Shims (SetShim): served online too, at once, then replaced by the live page.

The worker runs only in a secure context (HTTPS or localhost). Everywhere else the API does nothing.

Configure the module

Declaring PageOffline generates a WithOffline option with that page's route:

// PageOffline is /offline
type PageOffline struct{ App *App }

func (PageOffline) GET(r *http.Request) (body datapages.Component, err error) {
	return pageOffline(), nil
}

opts := []datapages.ServerOption{
	// Self-host Datastar: the CDN is unreachable offline.
	datapages.WithDatastarJS(assets.Path("datastar.js")),
	datapagesgen.WithOffline(app.OfflineConfig()),
}

// OfflineWorkerVersion identifies the installed worker and its cache. Increment
// it after a Datapages upgrade or a change to Assets, ExcludePaths,
// CrossOriginDestinations, OfflineClass, or PageOffline. Changes to Assets or
// PageOffline require a new installation because the worker fetches them only
// during installation.
const OfflineWorkerVersion = 1

func OfflineConfig() offline.Config {
	return offline.Config{
		WorkerVersion: OfflineWorkerVersion,
		// Precache the files required to render cached pages offline.
		Assets: []string{
			assets.Path("style.css"), assets.Path("datastar.js"),
		},
	}
}

For shims without PageOffline, install the module directly:

offline.WithServiceWorker("", offline.Config{WorkerVersion: 1})

offline.Config field	default
WorkerVersion	1; increment after a Datapages upgrade or a change to Assets, ExcludePaths, CrossOriginDestinations, OfflineClass, or PageOffline
ScriptURL	/service-worker.js; the scope is the whole origin either way
Assets	none; files cached during installation
OfflineClass	is-offline, toggled on <html> while offline
CrossOriginDestinations	image, style, script, font; empty non-nil disables
ExcludePaths	none; same-origin prefixes never cached