Note: This feature is available in Web Workers.
The ServiceWorker interface of the browsing contexts (e.g. pages, workers, etc.) can be associated with the same service worker, each through a unique ServiceWorker object.
A ServiceWorker object is available via a number of properties:
ServiceWorkerRegistration.activeServiceWorkerGlobalScope.serviceWorkerServiceWorkerContainer.controller — when the service worker is in activating or activated stateServiceWorkerRegistration.installing — when the service worker is in installing stateServiceWorkerRegistration.waiting — when the service worker is in installed stateThe statechanged event can be used to check and observe changes in the lifecycle-state of the object's associated service worker.
Related lifecycle events, such as activate are fired at the service worker itself.
Service workers allow static import of import.
Dynamic import is disallowed by the specification — calling import() will throw.
Service workers can only be registered in the Window scope in some or all browsers, because the ServiceWorker object is not exposed to SharedWorkerGlobalScope.
Check the browser compatibility for information.
The ServiceWorker interface inherits properties from its parent, EventTarget.
ServiceWorker.scriptURL Read onlyReturns the ServiceWorker serialized script URL defined as part of ServiceWorkerRegistration. The URL must be on the same origin as the document that registers the ServiceWorker.
ServiceWorker.state Read onlyReturns the state of the service worker. It returns one of the following values: parsed, installing, installed, activating, activated, or redundant.
The ServiceWorker interface inherits methods from its parent, EventTarget.
ServiceWorker.postMessage()Sends a message — consisting of any message event on its global scope.
statechangeFired when ServiceWorker.state changes.
errorFired when an error happens inside the ServiceWorker object.
This code snippet is from the live demo). The code listens for any change in the ServiceWorker.state and returns its value.
if ("serviceWorker" in navigator) {
navigator.serviceWorker
.register("service-worker.js", {
scope: "./",
})
.then((registration) => {
let 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", (e) => {
/ logState(e.target.state);
});
}
})
.catch((error) => {
/ Something went wrong during registration. The service-worker.js file
/ might be unavailable or contain a syntax error.
});
} else {
/ The current browser doesn't support service workers.
/ Perhaps it is too old or we are not in a Secure Context.
}
| Specification |
|---|
| Service Workers # serviceworker-interface |