ServiceWorker.onstatechange

Baseline Widely available

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

Обработчик события, вызываемый при срабатывании события statechange; по сути, срабатывает при изменении ServiceWorker.state.

Синтаксис

ServiceWorker.onstatechange = function(statechangeevent) { ... }
ServiceWorker.addEventListener('statechange', function(statechangeevent) { ... } )

Примеры

Данный фрагмент кода из примера событий service worker (демо) возвращает состояние при каждом его изменении.

js
var serviceWorker;
if (registration.installing) {
  serviceWorker = registration.installing;
  document.querySelector("#kind").textContent = "installing";
} else if (registration.waiting) {
  serviceWorker = registration.waiting;
  document.querySelector("#kind").textContent = "waiting";
} else if (registration.active) {
  serviceWorker = registration.active;
  document.querySelector("#kind").textContent = "active";
}

if (serviceWorker) {
  logState(serviceWorker.state);
  serviceWorker.addEventListener("statechange", function (e) {
    logState(e.target.state);
  });
}

Обратите внимание, что при срабатывании statechange, ссылки на service worker могли измениться. Например:

js
navigator.serviceWorker.register(..).then(function(swr) {
  swr.installing.state == "installing"
  swr.installing.onstatechange = function() {
    swr.installing == null;
    // At this point, swr.waiting OR swr.active might be true. This is because the statechange
    // event gets queued, meanwhile the underlying worker may have gone into the waiting
    // state and will be immediately activated if possible.
  }
})

Спецификации

Specification
Service Workers
# dom-serviceworker-onstatechange

Совместимость с браузерами

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