ServiceWorkerContainer: ready property

Baseline

Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since April 2018.

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Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is available in Web Workers.

The ready read-only property of the ServiceWorkerContainer interface provides a way of delaying code execution until a service worker is active.

The property returns a Promise that will never reject, and which waits indefinitely until the ServiceWorkerRegistration associated with the current page has an active worker. Once that condition is met, it resolves with the ServiceWorkerRegistration.

Value

A Promise that will never reject, and which may eventually resolve with a ServiceWorkerRegistration when there is an active service worker.

Examples

Deferring code until there is an active service worker

if ("serviceWorker" in navigator) {
  navigator.serviceWorker.ready.then((registration) => {
    console.log(`A service worker is active: ${registration.active}`);

    // At this point, you can call methods that require an active
    // service worker, like registration.pushManager.subscribe()
  });
} else {
  console.error("Service workers are not supported.");
}