ServiceWorker.onstatechange

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这是一个实验中的功能
此功能某些浏览器尚在开发中,请参考浏览器兼容性表格以得到在不同浏览器中适合使用的前缀。由于该功能对应的标准文档可能被重新修订,所以在未来版本的浏览器中该功能的语法和行为可能随之改变。

一个 EventListener 联动的属性,其会被任何stagechange类型事件抛出时联动; 它也基本上能在任何时候ServiceWorker.state 改变时被抛出.

语法

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

示例

这段代码出自 service worker registration-events sample (live demo). 它会监听 ServiceWorker.state 的改变并返回它的值.

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);
  });
}

注意当statechange 抛出时, service worker的引用可能已经改变。例如:

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.
  }
})

规范

规范 状态 附注
Service Workers
ServiceWorker.onstatechange
Working Draft Initial definition

浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 40.0 44.0 (44.0)[1] 未实现 24 未实现
Feature Android Android Webview Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support 未实现 未实现 44.0 (44.0) (Yes) 未实现 ? 未实现 40.0

[1] Service workers (and Push) have been disabled in the Firefox 45 and 52 Extended Support Releases (ESR.)

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