PushManager.getSubscription()

实验性: 这是一项实验性技术
在将其用于生产之前，请仔细检查浏览器兼容性表格。

PushManager 接口的方法**PushManager.getSubscription()** 尝试获取已有的推送订阅。

它返回一个 Promise 用来 resolve 出一个包含现有订阅的详细信息的PushSubscription (en-US) 对象。如果不存在已有的推送订阅，返回 null。

语法

js
PushManager.getSubscription().then(function(pushSubscription) { ... } );

参数

无。

返回值

A Promise that resolves to a PushSubscription (en-US) object or null.

例子

这个代码片段来自 push messaging and notification sample. (没有能直接运行的例子.)

js
// We need the service worker registration to check for a subscription
navigator.serviceWorker.ready.then(function (serviceWorkerRegistration) {
  // Do we already have a push message subscription?
  serviceWorkerRegistration.pushManager
    .getSubscription()
    .then(function (subscription) {
      // Enable any UI which subscribes / unsubscribes from
      // push messages.
      var pushButton = document.querySelector(".js-push-button");
      pushButton.disabled = false;

      if (!subscription) {
        // We aren’t subscribed to push, so set UI
        // to allow the user to enable push
        return;
      }

      // Keep your server in sync with the latest subscriptionId
      sendSubscriptionToServer(subscription);

      showCurlCommand(subscription);

      // Set your UI to show they have subscribed for
      // push messages
      pushButton.textContent = "Disable Push Messages";
      isPushEnabled = true;
    })
    .catch(function (err) {
      window.Demo.debug.log("Error during getSubscription()", err);
    });
});

规范

Specification
Push API
# dom-pushmanager-getsubscription

浏览器兼容性

BCD tables only load in the browser