croner

What is croner?

The croner npm package is a high-performance task scheduler for Node.js that allows you to run tasks at specific times or intervals. It is designed to be a drop-in replacement for the 'cron' package with additional features and improvements.

What are croner's main functionalities?

Simple cron job scheduling

This feature allows you to schedule a task to run at intervals defined by the cron syntax. In the provided code sample, a job is scheduled to run every 5 seconds.

const { Cron } = require('croner');

const job = Cron('*/5 * * * * *', () => {
  console.log('This will run every 5 seconds');
});

One-time execution

This feature allows you to schedule a task to run once at a specific time in the future. The code sample schedules a job to run once after 10 seconds.

const { Cron } = require('croner');

const job = Cron(new Date(Date.now() + 10000), () => {
  console.log('This will run once after 10 seconds');
});

Stopping a job

This feature allows you to stop a scheduled job. In the code sample, a job is scheduled to run every 5 seconds but is stopped after 15 seconds.

const { Cron } = require('croner');

const job = Cron('*/5 * * * * *', () => {
  console.log('This job will be stopped.');
});

setTimeout(() => {
  job.stop();
}, 15000);

Timezone support

This feature allows you to schedule jobs according to a specific timezone. The code sample schedules a job to run at 10:30 AM in the 'America/New_York' timezone.

const { Cron } = require('croner');

const job = Cron('0 30 10 * * *', () => {
  console.log('This will run at 10:30 AM in the America/New_York timezone.');
}, { timezone: 'America/New_York' });

Other packages similar to croner

node-schedule

node-schedule is a flexible cron-like and not-cron-like job scheduler for Node.js. It allows you to schedule jobs using both cron-style and human-readable syntax. It is similar to croner but offers a different API and additional scheduling features like scheduling jobs with JavaScript Date objects.

agenda

agenda is a job scheduling library for Node.js that uses MongoDB for persisting job data. It is more suitable for distributed or long-running job tasks. Unlike croner, which focuses on in-memory cron job scheduling, agenda provides persistence and is better suited for applications that require job recovery and failover capabilities.

bull

bull is a Redis-based queue system for Node.js. It is designed for handling distributed jobs and messages in Node.js applications. While croner is used for scheduling tasks, bull is more focused on job queuing, processing, and concurrency, making it suitable for more complex job handling scenarios.

README

Trigger functions or evaluate cron expressions in JavaScript or TypeScript. No dependencies. Most features. Node. Deno. Bun. Browser.

Try it live on jsfiddle.

Croner

• Trigger functions in JavaScript using Cron syntax.
• Find the first date of the next month, the date of the next Tuesday, etc.
• Pause, resume, or stop execution after a task is scheduled.
• Works in Node.js >=7.6 (both require and import).
• Works in Deno >=1.16.
• Works in Bun >=0.2.2
• Works in browsers as standalone, UMD or ES-module.
• Works with both JavaScriptCore and V8.
• Schedule using specific target time zones.
• Includes TypeScript typings.

Quick examples:

// Basic: Run a function at the interval defined by a cron expression
const job = Cron('*/5 * * * * *', () => {
	console.log('This will run every fifth second');
});

// Enumeration: What dates do the next 100 sundays occur at?
const nextSundays = Cron('0 0 0 * * 7').enumerate(100);
console.log(nextSundays);

// Days left to a specific date
const msLeft = Cron('59 59 23 24 DEC *').next() - new Date();
console.log(Math.floor(msLeft/1000/3600/24) + " days left to next christmas eve");

// Run a function at a specific date/time using a non-local timezone (time is ISO 8601 local time)
// This will run 2023-01-23 00:00:00 according to the time in Asia/Kolkata
Cron('2023-01-23T00:00:00', { timezone: 'Asia/Kolkata' }, () => { console.log('Yay') });

More examples...

Why another JavaScript cron implementation

Because the existing ones are not good enough. They have serious bugs, use bloated dependencies, do not work in all environments, and/or simply do not work as expected.

	croner	cronosjs	node-cron	cron	node-schedule
Platforms
Node.js (CommonJS)	✓	✓	✓	✓	✓
Browser (ESMCommonJS)	✓	✓
Deno (ESM)	✓
Features
Typescript typings	✓	✓
dom-AND-dow	✓
dom-OR-dow	✓	✓	✓	✓	✓
Next run	✓	✓		✓	✓
Next n runs	✓	✓		✓
Timezone	✓	✓	✓	✓	✓
Minimum interval	✓
Controls (stop/resume)	✓	✓	✓	✓	✓
Range (0-13)	✓	✓	✓	✓	✓
Stepping (*/5)	✓	✓	✓	✓	✓
Last day of month (L)	✓	✓

In depth comparison of various libraries

	croner	cronosjs	node-cron	cron	node-schedule
Size
Minified size (KB)	15.5	16.3	16.5	-	-
Bundlephobia minzip (KB)	3.6	5.1	5.7	23.9	32.4
Dependencies	0	0	1	1	3
Popularity
Downloads/week 1	672K	30K	376K	1574K	804K
Quality
Issues 1	0	2	118 :warning:	119 :warning:	135 :warning:
Code coverage	99%	98%	100%	81%	94%
Performance
Ops/s 1 2 3 4 5 6	99 952	49 308	N/A :x:	Test failed :x:	2 299 :warning:
Ops/s 0 0 0 29 2 *	65 392	17 138	N/A :x:	Test failed :x:	1 450 :warning:
Tests	8/8	7/8	0/8 2 :question:	1/8 :warning:	7/8
Test 0 0 23 * * *	2022-10-09 00:40	2022-10-09 00:40	N/A	2022-10-09 00:40	2022-10-09 00:40
Test 0 0 0 L 2 * 3	2023-02-28 00:00	2023-02-28 00:00	N/A	N/A	2023-02-28 00:00
Test 0 0 0 29 2 *	2024-02-29 00:00	2024-02-29 00:00	N/A	2023-03-29 00:00 :x:	2024-02-29 00:00
Test 0 0 0 29 2 6 4	2048-02-09 00:00	N/A	N/A	N/A	N/A
Test 0 0 0 15 2 *	2023-02-16 00:00	2023-02-16 00:00	N/A	2023-03-15 00:00 :x:	2023-02-16 00:00
Test 0 0 0 * 10 1	2022-10-10 00:00	2022-10-10 00:00	N/A	2022-11-07 00:00 :x:	2022-10-10 00:00
Test 0 0 23 31 3 *	2023-03-31 23:00	2023-03-31 23:00	N/A	2023-04-01 23:00 :x:	2023-03-31 23:00
Test 1 2 3 4 5 6	2023-05-04 03:02	2023-05-04 03:02	N/A	2023-06-03 03:02 :x:	2023-05-04 03:02

Note

• Table last updated at 2022-10-23
• node-cron has no interface to predict when the function will run, so tests cannot be carried out.
• All tests and benchmarks were carried out using https://github.com/Hexagon/cron-comparison

Installation

Node.js

npm install croner --save

JavaScript

// ESM Import ...
import Cron from "croner";

// ... or CommonJS Require
const Cron = require("croner");

TypeScript

Notes for TypeScript:

• If using strict eslint rules, specifically new-cap combined with no-new, you need to import and use lowercase cron instead of { Cron }.

import { Cron } from "croner";

const job : Cron = new Cron("* * * * * *", () => {
	console.log("This will run every second.");
});

Bun

bun add croner

Note If you encounter problems during installation, try using bun add croner --backend=copyfile.

import Cron from "croner";

Deno

JavaScript

import Cron from "https://deno.land/x/croner@5.6.2/src/croner.js";

Cron("* * * * * *", () => {
	console.log("This will run every second.");
});

TypeScript

import { Cron } from "https://deno.land/x/croner@5.6.2/src/croner.js";

const _scheduler : Cron = new Cron("* * * * * *", () => {
	console.log("This will run every second.");
});

Browser

Manual

• Download the latest zipball.
• Unpack the zip file.
• Grab croner.min.js (UMD and standalone) or croner.min.mjs (ES-module) from the dist/ folder.

CDN

To use as a UMD-module (stand alone, RequireJS etc.)

<script src="https://cdn.jsdelivr.net/npm/croner@5/dist/croner.min.js"></script>

To use as an ES-module

<script type="module">
	import Cron from "https://cdn.jsdelivr.net/npm/croner@5/dist/croner.min.mjs";

	// ... see usage section ...
</script>

Documentation

Full documentation available at hexagon.github.io/croner.

The short version:

Signature

Cron takes three arguments

• pattern
• options (optional)
• scheduled function (optional)

const job = Cron("* * * * * *" /* Or a date object, or ISO 8601 local time */ , /*optional*/ { maxRuns: 1 } , /*optional*/ () => {} );

// If function is omitted in constructor, it can be scheduled later
job.schedule((/* optional */ job, /* optional */ context) => {});		

// States
const nextRun = job.next( /*optional*/ previousRun );	// Get a Date object representing next run
const nextRuns = job.enumerate(10, /*optional*/ startFrom ); // Get a array of Dates, containing next 10 runs according to pattern
const prevRun = job.previous( );	
const msToNext = job.msToNext( /*optional*/ previousRun ); // Milliseconds left to next execution
const isRunning = job.running();

// Control scheduled execution
job.pause();				
job.resume();
job.stop();

Options

Key	Default value	Data type	Remarks
name	undefined	String	If you specify a name for the job, Croner will keep a reference to the job in exported array scheduledJobs
maxRuns	Infinite	Number
catch	false	Boolean	Catch unhandled errors in triggered function. Passing true will silently ignore errors. Passing a callback function will trigger this callback on error.
timezone	undefined	String	Timezone in Europe/Stockholm format
startAt	undefined	String	ISO 8601 formatted datetime (2021-10-17T23:43:00) in local time (according to timezone parameter if passed)
stopAt	undefined	String	ISO 8601 formatted datetime (2021-10-17T23:43:00) in local time (according to timezone parameter if passed)
interval	0	Number	Minimum number of seconds between triggers.
paused	false	Boolean	If the job should be paused from start.
context	undefined	Any	Passed as the second parameter to triggered function
legacyMode	true	boolean	Combine day-of-month and day-of-week using true = OR, false = AND
unref	false	boolean	Setting this to true unrefs the internal timer, which allows the process to exit even if a cron job is running.
utcOffset	undefined	boolean	Schedule using a specific utc offset in minutes. *This does not take care of daylight savings time, you probably want to use option timezone instead.

Warning Unreferencing timers (option unref) is only supported by Node.js and Deno. Browsers have not yet implemented this feature, and it does not make sense to use it in a browser environment.

Pattern

The expressions used by Croner are very similar to those of Vixie Cron, but with a few additions and changes as outlined below:

• Croner expressions have the following additional modifiers:

  • ? A question mark is substituted with the time of Croner's initialization. For example ? ? * * * * would be substituted with 25 8 * * * * if the time is <any hour>:08:25 at the time of new Cron('? ? * * * *', <...>). The question mark can be used in any field.
  • L L can be used in the day of the month field to specify the last day of the month.

• Croner allows you to pass a JavaScript Date object or an ISO 8601 formatted string as a pattern. The scheduled function will trigger at the specified date/time and only once. If you use a timezone different from the local timezone, you should pass the ISO 8601 local time in the target location and specify the timezone using the options (2nd parameter).

• Croner also allows you to change how the day-of-week and day-of-month conditions are combined. By default, Croner (and Vixie cron) will trigger when either the day-of-month OR the day-of-week conditions match. For example, 0 20 1 * MON will trigger on the first of the month as well as each Monday. If you want to use AND (so that it only triggers on Mondays that are also the first of the month), you can pass { legacyMode: false }. For more information, see issue #53.

// ┌──────────────── (optional) second (0 - 59)
// │ ┌────────────── minute (0 - 59)
// │ │ ┌──────────── hour (0 - 23)
// │ │ │ ┌────────── day of month (1 - 31)
// │ │ │ │ ┌──────── month (1 - 12, JAN-DEC)
// │ │ │ │ │ ┌────── day of week (0 - 6, SUN-Mon) 
// │ │ │ │ │ │       (0 to 6 are Sunday to Saturday; 7 is Sunday, the same as 0)
// │ │ │ │ │ │
// * * * * * *

Field	Required	Allowed values	Allowed special characters	Remarks
Seconds	Optional	0-59	* , - / ?
Minutes	Yes	0-59	* , - / ?
Hours	Yes	0-23	* , - / ?
Day of Month	Yes	1-31	* , - / ? L
Month	Yes	1-12 or JAN-DEC	* , - / ?
Day of Week	Yes	0-7 or SUN-MON	* , - / ?	0 to 6 are Sunday to Saturday 7 is Sunday, the same as 0

Note Weekday and month names are case-insensitive. Both MON and mon work.

It is also possible to use the following "nicknames" as pattern.

Nickname	Description
@yearly	Run once a year, ie. "0 0 1 1 *".
@annually	Run once a year, ie. "0 0 1 1 *".
@monthly	Run once a month, ie. "0 0 1 * *".
@weekly	Run once a week, ie. "0 0 * * 0".
@daily	Run once a day, ie. "0 0 * * *".
@hourly	Run once an hour, ie. "0 * * * *".

Examples

Expressions

// Run a function according to pattern
Cron('15-45/10 */5 1,2,3 ? JAN-MAR SAT', { legacyMode: false }, function () {
	console.log('This will run every tenth second between second 15-45');
	console.log('every fifth minute of hour 1,2 and 3 when day of month');
	console.log('is the same as when Cron started, every saturday in January to March.');
});

Interval

// Trigger on specific interval combined with cron expression
Cron('* * * 7-16 * MON-FRI', { interval: 90, legacyMode: false }, function () {
	console.log('This will trigger every 90th second at 7-16 on mondays to fridays.');
});

Find dates

// Find next month
const nextMonth = Cron("@monthly").next(),
	nextSunday = Cron("@weekly").next(),
	nextSat29feb = Cron("0 0 0 29 2 6", { legacyMode: false }).next(),
	nextSunLastOfMonth = Cron("0 0 0 L * 7", { legacyMode: false }).next();

console.log("First day of next month: " +  nextMonth.toLocaleDateString());
console.log("Next sunday: " +  nextSunday.toLocaleDateString());
console.log("Next saturday at 29th of february: " +  nextSat29feb.toLocaleDateString());  // 2048-02-29
console.log("Next month ending with a sunday: " +  nextSunLastOfMonth.toLocaleDateString()); 

With options

const job = Cron(
	'* * * * *', 
	{ 
		maxRuns: Infinity, 
		startAt: "2021-11-01T00:00:00", 
		stopAt: "2021-12-01T00:00:00",
		timezone: "Europe/Stockholm"
	},
	function() {
		console.log('This will run every minute, from 2021-11-01 to 2021-12-01 00:00:00');
	}
);

Job controls

const job = Cron('* * * * * *', (self) => {
	console.log('This will run every second. Pause on second 10. Resume on 15. And quit on 20.');
	console.log('Current second: ', new Date().getSeconds());
	console.log('Previous run: ' + self.previous());
	console.log('Next run: ' + self.next());
});

Cron('10 * * * * *', {maxRuns: 1}, () => job.pause());
Cron('15 * * * * *', {maxRuns: 1}, () => job.resume());
Cron('20 * * * * *', {maxRuns: 1}, () => job.stop());

Passing a context

const data = {
	what: "stuff"
};

Cron('* * * * * *', { context: data }, (_self, context) => {
	console.log('This will print stuff: ' + context.what);
});

Cron('*/5 * * * * *', { context: data }, (self, context) => {
	console.log('After this, other stuff will be printed instead');
	context.what = "other stuff";
	self.stop();
});

Fire on a specific date/time

// A javascript date, or a ISO 8601 local time string can be passed, to fire a function once. 
// Always specify which timezone the ISO 8601 time string has with the timezone option.
let job = Cron("2025-01-01T23:00:00",{timezone: "Europe/Stockholm"},() => {
	console.log('This will run at 2025-01-01 23:00:00 in timezone Europe/Stockholm');
});

if (job.next() === null) {
	// The job will not fire for some reason
} else {
	console.log("Job will fire at " + job.next());
}

Naming jobs

If you provide a name for the job using the option { name: '...' }, a reference to the job will be stored in the exported array scheduledJobs. Naming a job makes it accessible throughout your application.

Note If a job is stopped using .stop(), and goes out of scope, it will normally be eligible for garbage collection and will be deleted during the next garbage collection cycle. Keeping a reference by specifying option name prevents this from happening.

// import { Cron, scheduledJobs } ...

// Scoped job
(() => {

	// As we specify a name for the job, a reference will be kept in `scheduledJobs`
	const job = Cron("* * * * * *", { name: "Job1" }, function () {
		console.log("This will run every second");
	});

	job.pause();
	console.log("Job paused");

})();

// Another scope, delayed 5 seconds
setTimeout(() => {

	// Find our job
	// - scheduledJobs can either be imported separately { Cron, scheduledJobs }
	//   or access through Cron.scheduledJobs
	const job = scheduledJobs.find(j => j.name === "Job1");

	// Resume it
	if (job) {
		if(job.resume()) {
			// This will happen
			console.log("Job resumed successfully");
		} else {
			console.log("Job found, but could not be restarted. The job were probably stopped using `.stop()` which prevents resuming.");
		}
	} else {
		console.error("Job not found");
	}

}, 5000);

Act at completion

// Start a job firing once each 5th second, run at most 3 times
const job = new Cron("0/5 * * * * *", { maxRuns: 3 }, (job) => {
    
    // Do work
    console.log('Job Running');

    // Is this the last execution?
    if (!job.next()) {
        console.log('Last execution');
    }

});
 
// Will there be no executions? 
// This would trigger if you change maxRuns to 0, or manage to compose 
// an impossible cron expression.
if (!job.next() && !job.previous()) {
    console.log('No executions scheduled');
}

Contributing

See Contribution Guide

... or ...

License

MIT License

Footnotes

1. As of 2022-10-08 ↩ ↩²

2. Node-cron has no way of showing next run time. ↩

3. Requires support for L-modifier ↩

4. In dom-AND-dow mode, only supported by croner at the moment. ↩