Chrome Extension | Multiple alarms going off at once

Question

I am creating a task reminder extension. The user has an option to keep adding tasks and set reminders for each task. I am using chrome.storage to store these tasks and using onChanged listener on storage to create an alarm for each task added to the storage. But the issue is that if I set a reminder of 2 mins for a task and 3 mins for another task. Then at the end of 2 mins I am getting notification for both the tasks and at the end of 3mins I again get notifications for both the tasks.

background.js

chrome.storage.onChanged.addListener(function(changes, namespace) {
let id = (changes.tasks.newValue.length)-1
let data = changes.tasks.newValue[id]

if(data.task && data.hrs && data.min){
    let totalMins = (parseInt(data.hrs*60))+parseInt(data.min)
    let alarmTime = 60*1000*totalMins
    chrome.alarms.create("remind"+id,{when:Date.now() + alarmTime})
}

chrome.alarms.onAlarm.addListener(()=>{
    let notifObj = {
        type: "basic",
        iconUrl:"./images/logo5.png",
        title: "Time to complete you  task",
        message: data.task
    }
    chrome.notifications.create('remindNotif'+id, notifObj)
})

popup.js

let hrs = document.querySelector("#time-hrs")
let min = document.querySelector("#time-min")
let submitBtn = document.querySelector("#submitBtn")
let task = document.querySelector("#task")


hrs.value = 0;
min.value = 1


hrs.addEventListener('change',()=>{
  if (hrs.value < 0){
    hrs.value =0;
  }
})

min.addEventListener('change',()=>{
   if (min.value < 1){
      min.value = 1;
   }
})

submitBtn.addEventListener("click", ()=>{
 if(task.value){
    chrome.storage.sync.get('tasks',(item)=>{

        let taskArr = item.tasks ? item.tasks : []
        linkArr.push({task:task.value, hrs:hrs.value, min:min.value})
        chrome.storage.sync.set({ 'tasks' : taskArr })
    })
  };
 });

manifest.json

{
    "name" : "Link Snooze",
    "description" : "This extension reminds you to open your saved links",
    "manifest_version":2,
    "version":"0.1.0",
    "icons":{
        "16":"./images/logo5.png",
        "48":"./images/logo5.png",
        "128":"./images/logo5.png"
    },
    "browser_action":{
        "default_popup":"popup.html",
        "default_icon":"./images/logo5.png"
    },
    "permissions":["storage", "notifications","alarms"],
    "background" : {
        "scripts": ["background.js"],
        "persistent" : false
    },
    "options_page":"options.html"
}

wOxxOm · Accepted Answer · 2022-02-05T14:34:47.810

Problem.

You register a new onAlarms listener when the storage changes in addition to the old listeners. All of them run each time one alarm is triggered.

Solution.

When using a non-persistent background script, all API listeners must be registered just once for the same function and it must be done synchronously, not inside an asynchronous callback or await or then(), otherwise the event will be lost when the background script auto-terminates and then wakes up for this event. The convention is to do it at the beginning of the script. The reason it worked for you until now is that the background script is kept alive while the popup is open or while devtools for the background script was open.

Such listeners evidently won't be able to use the variables from an asynchronous callback directly like data.task in your code. The solution is to use a different method of attaching data to an event, for example, create the alarm with a name that already contains the data, specifically data.task.

chrome.alarms.create(data.task, {delayInMinutes: hrs * 60 + min});

onAlarm event provides the alarm as a parameter so you can use its name, see the documentation.

Random hints:

An object can be used as an alarm name if you call JSON.stringify(obj) when creating and JSON.parse(alarm.name) in onAlarm.
In the popup, instead of manually adjusting out-of-range values, use a number input in html:
```
<input id="time-min" type=number min=0 max=59 step=1>
```
Then read it as a number: document.querySelector("#time-min").valueAsNumber || 0

Chrome Extension | Multiple alarms going off at once

1 Answers1