@saverious/cronjob

A job scheduler to define time when a task or tasks should execute

Installation

   npm i @saverious/cronjob

Usage

ESM syntax

    /**
     * cron.addJob      - returns jobID as string
     * cron.addSchedule - returns scheduleID as string
    */
    import { Cron } from '@saverious/cronjob';

    function add(a, b) {
        console.log(`a: ${a}\nb: ${b}`);
        console.log('sum: ', a + b);
    }

    function main () {
        const now = new Date();
        const time = {
            year: now.getFullYear(),
            month: now.getMonth() + 1,
            day: now.getDate(),
            hour: now.getHours(),
            minute: now.getMinutes() + 1
        };

        const cron = new Cron({executeMissedSchedules: false});
        const jobID = cron.addJob('add', () => add(3, 4));
        cron.addSchedule(jobID, time);
        cron.runScheduler();
    }

    main();

CJS syntax

    /**
     * cron.addJob      - returns jobID as string
     * cron.addSchedule - returns scheduleID as string
    */
    const { Cron } = require('@saverious/cronjob');

    function add(a, b) {
        console.log(`a: ${a}\nb: ${b}`);
        console.log('sum: ', a + b);
    }

    function main () {
        const now = new Date();
        const time = {
            year: now.getFullYear(),
            month: now.getMonth() + 1,
            day: now.getDate(),
            hour: now.getHours(),
            minute: now.getMinutes() + 1
        };

        const cron = new Cron({executeMissedSchedules: false});
        const jobID = cron.addJob('add', () => add(3, 4));
        cron.addSchedule(jobID, time);
        cron.runScheduler();
    }

    main();

Cron class

This library exposes a class - Cron - that is used to handle the scheduling. Cron is declared with an optional argument - {executeMissedSchedules: boolean} - that defines how skipped tasks are handled.

const cron = new Cron({executeMissedSchedules: false});

In this case, skipped tasks are those whose time of schedule has passed without them being executed.

Passing true: The skipped task will be executed
Passing false: The skipped task will be deleted

If no argument is defined, the 'executeMissedSchedules' flag defaults to false. The default operation is deletion of the skipped task.

Methods

Cron.addJob(jobName: string, func: Function)

This method defines the name of the task you want to schedule and its corresponding function. The name must be unique. The function returns a job id that uniquely identifies the task.

const jobID = cron.addJob('add', () => add(3, 4));

NOTE: Multiple jobs can be defined too. For instance:

// ... define cron Class
const jobID1 = cron.addJob('job1', () => add(3, 4));
const jobID2 = cron.addJob('job2', () => multiply(3, 4));
const jobID3 = cron.addJob('job3', () => subtract(3, 4));
// ... continue

Cron.addSchedule(jobID: string, time: Object)

This method defines the specific time you want the task to run. The task is identified by the job id from Cron.addJob(). This job id is passed to Cron.addSchedule() as the first parameter.

const scheduleID = cron.addSchedule(jobID, time);

The method returns a schedule id that uniquely identifies the schedule.

NOTE: Multiple schedules can be defined for a single job. For example:

// ... define cron Class and schedules(time)
cron.addSchedule(job1, time1);
cron.addSchedule(job1, time2);
cron.addSchedule(job1, time3);
// ... continue

cron.runScheduler()

This method starts the scheduler. It listens for each schedule and executes each task when its respective scheduled time is reached.

cron.runScheduler();