Job Scheduler ​

Overview ​

@webext-core/job-scheduler uses the alarms API to manage different types of reoccuring jobs:

• One-time jobs
• Jobs that run on an interval
• Cron jobs

Installation ​

NPM ​

pnpm i @webext-core/job-scheduler

import { defineJobScheduler } from '@webext-core/job-scheduler';

CDN ​

curl -o job-scheduler.js https://cdn.jsdelivr.net/npm/@webext-core/job-scheduler/lib/index.global.js

<script src="/job-scheduler.js"></script>
<script>
  const { defineJobScheduler } = webExtCoreJobScheduler;
</script>

Usage ​

defineJobSchduler should to be executed once in the background. It returns an object that can be used to schedule or remove jobs.

import { defineJobScheduler } from '@webext-core/job-scheduler';

const jobs = defineJobScheduler();

Once the job scheduler is created, call scheduleJob. To see all the options for configuring jobs, see the API reference.

jobs.scheduleJob({
  id: 'job1',
  type: 'once',
  date: Date.now() + 1.44e7, // In 4 hours
  execute: () => {
    console.log('Executed job once');
  },
});

jobs.scheduleJob({
  id: 'job2',
  type: 'interval',
  interval: DAY, // Runs every 24 hours
  execute: () => {
    console.log('Executed job on interval');
  },
});

jobs.scheduleJob({
  id: 'job3',
  type: 'cron',
  expression: '0 */2 * * *', // https://crontab.guru/#0_*/2_*_*_*
  execute: () => {
    console.log('Executed CRON job');
  },
});

If a job has been created in the past, and nothing has changed, scheduleJob will do nothing. If something changed, it will update the job.

To stop running a job, call removeJob.

job.removeJob('some-old-job');

Parameterized Jobs ​

You can't pass parameters into each individual job execution, but you can pass dependencies when scheduling a job by using higher-order functions:

import { someJob } from './someJob.ts';

// Create your dependency
const someDependency = new SomeDependency();

const jobs = defineJobScheduler();
jobs.scheduleJob({
  // ...
  execute: someJob(someDependency),
});

function someJob(someDependency: SomeDependency) {
  return async () => {
    // Use someDependency
  };
}

Other JS Contexts ​

You should only create one scheduler, and it should be created in the background page/service worker.

To schedule jobs from a UI or content script, you can use @webext-core/proxy-service.

import { defineProxyService } from '@webext-core/proxy-service';

export const [registerJobScheduler, getJobScheduler] = defineProxyService('JobScheduler', () =>
  defineJobScheduler(),
);

import { registerJobScheduler } from './job-scheduler';

const jobs = registerJobScheduler();

// Schedule any jobs in the background
jobs.scheduleJob({
  // ...
});

import { getJobScheduler } from './job-scheduler';

// Get a proxy instance and use it to schedule more jobs
const jobs = getJobScheduler();
jobs.scheduleJob({
  // ...
});