[SW-tutorial] Refactor alarms API logic (sw-tips.js) (GoogleChrome#865)

* [SW-tutorial] Refactor alarms API logic

After doing some experiments (like closing all my browser windows which I never, EVER do...) I realized the tips logic was not working as expected, because [alarms do not persist across browser sessions[(https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/alarms#:~:text=Alarms%20do%20not%20persist%20across%20browser%20sessions.)

* Return storage set

* Tech review

Author: AmySteam

functional-samples/tutorial.quick-api-reference/sw-tips.js

@@ -5,16 +5,25 @@ const updateTip = async () => {
   const response = await fetch('https://extension-tips.glitch.me/tips.json');
   const tips = await response.json();
   const randomIndex = Math.floor(Math.random() * tips.length);
-  await chrome.storage.local.set({ tip: tips[randomIndex] });
+  return chrome.storage.local.set({ tip: tips[randomIndex] });
 };
 
-// Create a daily alarm and retrieves the first tip when extension is installed.
-chrome.runtime.onInstalled.addListener(({ reason }) => {
-  if (reason === 'install') {
-    chrome.alarms.create({ delayInMinutes: 1, periodInMinutes: 1440 });
+const ALARM_NAME = 'tip';
+
+// Check if alarm exists to avoid resetting the timer.
+// The alarm might be removed when the browser session restarts.
+async function createAlarm() {
+  const alarm = await chrome.alarms.get(ALARM_NAME);
+  if (typeof alarm === 'undefined') {
+    chrome.alarms.create(ALARM_NAME, {
+      delayInMinutes: 1,
+      periodInMinutes: 1440
+    });
     updateTip();
   }
-});
+}
+
+createAlarm();
 
 // Retrieve tip of the day
 chrome.alarms.onAlarm.addListener(updateTip);