From 33058f2b292b3a581333bdfb21b8f671898c5060 Mon Sep 17 00:00:00 2001
From: Peter Bengtsson <mail@peterbe.com>
Date: Tue, 8 Dec 2020 14:40:17 -0500
Subject: initial commit

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+---
+title: PushManager.getSubscription()
+slug: Web/API/PushManager/getSubscription
+tags:
+  - API
+  - PushManager
+  - Service Worker
+  - 实验中的
+  - 方法
+translation_of: Web/API/PushManager/getSubscription
+---
+<p>{{SeeCompatTable}}{{ApiRef("Push API")}}</p>
+
+<p>{{domxref("PushManager")}} 接口的方法<strong><code>PushManager.getSubscription()</code></strong> 尝试获取已有的推送订阅。</p>
+
+<p>它返回一个 {{jsxref("Promise")}} 用来resolve出一个包含现有订阅的详细信息的{{domxref("PushSubscription")}} 对象。如果不存在已有的推送订阅，返回null。</p>
+
+<h2 id="语法">语法</h2>
+
+<pre class="brush: js notranslate" style="font-size: 14px;">​PushManager.getSubscription().then(function(pushSubscription) { ... } );</pre>
+
+<h3 id="参数">参数</h3>
+
+<p>无。</p>
+
+<h3 id="返回值">返回值</h3>
+
+<p>A {{jsxref("Promise")}} that resolves to a {{domxref("PushSubscription")}} object or <code>null</code>.</p>
+
+<h2 id="例子">例子</h2>
+
+<p>这个代码片段来自 <a href="https://github.com/GoogleChrome/samples/blob/gh-pages/push-messaging-and-notifications">push messaging and notification sample</a>. (没有能直接运行的例子.)</p>
+
+<pre class="brush: js notranslate" style="font-size: 14px;">// 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);
+      });
+  });
+</pre>
+
+<h2 id="说明">说明</h2>
+
+<table class="standard-table">
+ <tbody>
+  <tr>
+   <th scope="col">说明</th>
+   <th scope="col">状态</th>
+   <th scope="col">注释</th>
+  </tr>
+  <tr>
+   <td>{{SpecName('Push API', '#widl-PushManager-getSubscription-Promise-PushSubscription', 'getSubscription()')}}</td>
+   <td>{{Spec2('Push API')}}</td>
+   <td>最初的定义</td>
+  </tr>
+ </tbody>
+</table>
+
+<h2 id="支持的浏览器">支持的浏览器</h2>
+
+<div>
+<div>
+<div class="hidden">这个支持的浏览器列表是由结构化数据生成的。如果你想修改这个表格，请获取最新的代码并提交t<a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a> 。</div>
+
+<p>{{Compat("api.PushManager.getSubscription")}}</p>
+</div>
+</div>
+
+<div id="gtx-trans" style="position: absolute; left: 488px; top: 144px;">
+<div class="gtx-trans-icon"></div>
+</div>
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