未捕获（在承诺中）DOMException：订阅失败 - 没有活动的服务工作者

Question

I'm trying to subscribe the user but this is the error I get the first time. The second time, it is working because the user is already active

This is my code :

 if ('serviceWorker' in navigator) {
   console.log('Service Worker is supported');
   navigator.serviceWorker.register('sw.js').then(function(reg) {
     console.log(':^)', reg);
     reg.pushManager.subscribe({
       userVisibleOnly: true
     }).then(function(sub) {
       console.log('endpoint:', sub.endpoint);
       var div = document.getElementById('id');
       div.innerHTML = div.innerHTML + sub.endpoint;
       // var b = document.getElementsByTagName('body')[0];
       //b.appendChild(div);
       //alert(sub.endpoint);
     });
   });
 }

I already tried the following, but the ready.then() method is not happening:

 if ('serviceWorker' in navigator) {
   console.log('Service Worker is supported');
   navigator.serviceWorker.register('sw.js').then(function(sreg) {
     console.log(':^)', sreg);
     navigator.serviceWorker.ready.then(function(reg) {
       reg.pushManager.subscribe({
         userVisibleOnly: true
       }).then(function(sub) {
         console.log('endpoint:', sub.endpoint);
         var div = document.getElementById('id');
         div.innerHTML = div.innerHTML + sub.endpoint;
         // var b = document.getElementsByTagName('body')[0];
         //b.appendChild(div);
         //alert(sub.endpoint);
       });
     });
   });
 }

Any ideas ?

Answer 1

You should wait for the service worker to be activated before triggering the subscription.

use stateChange listener for figuring out if service worker is active

navigator.serviceWorker.register(workerFileName, {scope: "/"})
    .then(
    function (reg) {
        var serviceWorker;
        if (reg.installing) {
            serviceWorker = reg.installing;
            // console.log('Service worker installing');
        } else if (reg.waiting) {
            serviceWorker = reg.waiting;
            // console.log('Service worker installed & waiting');
        } else if (reg.active) {
            serviceWorker = reg.active;
            // console.log('Service worker active');
        }

        if (serviceWorker) {
            console.log("sw current state", serviceWorker.state);
            if (serviceWorker.state == "activated") {
                //If push subscription wasnt done yet have to do here
                console.log("sw already activated - Do watever needed here");
            }
            serviceWorker.addEventListener("statechange", function(e) {
                console.log("sw statechange : ", e.target.state);
                if (e.target.state == "activated") {
                    // use pushManger for subscribing here.
                    console.log("Just now activated. now we can subscribe for push notification")
                    subscribeForPushNotification(reg);
                }
            });
        }
    },
    function (err) {
        console.error('unsuccessful registration with ', workerFileName, err);
    }
);

Answer 2

You can resolve this by checking for service worker status. Perform your actions only when the service worker is active.

navigator.serviceWorker.register('sw.js').then(function(reg) {
 if(reg.installing) {
        console.log('Service worker installing');
    } else if(reg.waiting) {
        console.log('Service worker installed');
    } else if(reg.active) {
        console.log('Service worker active');
    }
 // Include below mentioned validations
}

Check for pushnotification is supported or not using

 // Check if push messaging is supported  
    if (!('PushManager' in window)) {  
       console.log('Push messaging isn\'t supported.');  
       return;  
     }
   //
   if (Notification.permission === 'denied') {  
      console.log('The user has blocked notifications.');  
      return;  
   }

After these two checks implement you functionality.

navigator.serviceWorker.ready.then(function(reg) {  .... })

Hope this helps