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

Try it live on jsfiddle, and check out the full documentation on croner.56k.guru.

Croner - Cron for JavaScript and TypeScript

• Trigger functions in JavaScript using Cron syntax.
• Evaluate cron expressions and get a list of upcoming run times.
• Supports seconds and year fields, L (last), W (weekday), # (nth occurrence), and + (AND logic).
• Works in Node.js >=18.0 (both require and import), Deno >=2.0 and Bun >=1.0.0.
• Works in browsers as standalone, UMD or ES-module.
• Target different time zones.
• Built-in overrun protection
• Built-in error handling
• Includes TypeScript typings.
• Support for asynchronous functions.
• Pause, resume, or stop execution after a task is scheduled.
• Operates in-memory, with no need for a database or configuration files.
• Zero dependencies.

Quick examples:

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

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

// Days left to a specific date
const msLeft = new Cron('59 59 23 24 DEC *').nextRun() - 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 2024-01-23 00:00:00 according to the time in Asia/Kolkata
new Cron('2024-01-23T00:00:00', { timezone: 'Asia/Kolkata' }, () => { console.log('Yay!') });

// Check if a date matches a cron pattern
const mondayCheck = new Cron('0 0 0 * * MON');
console.log(mondayCheck.match('2024-01-01T00:00:00')); // true  (Monday)
console.log(mondayCheck.match('2024-01-02T00:00:00')); // false (Tuesday)

More examples...

Installation

Full documentation on installation and usage is found at https://croner.56k.guru

Note
If you are migrating from a different library such as cron or node-cron, or upgrading from a older version of croner, see the migration section of the manual.

Install croner using your favorite package manager or CDN, then include it in you project:

Using Node.js or Bun

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

// ... or CommonJS Require, destructure to add type hints
const { Cron } = require("croner");

Using Deno

// From deno.land/x
import { Cron } from "https://deno.land/x/croner@10.0.0/dist/croner.js";

// ... or jsr.io
import { Cron } from "jsr:@hexagon/croner@10.0.0";

In a webpage using the UMD-module

<script src="https://cdn.jsdelivr.net/npm/croner@10/dist/croner.umd.min.js"></script>

Documentation

Signature

Cron takes three arguments

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

// Parameters
// - First: Cron pattern, js date object (fire once), or ISO 8601 time string (fire once)
// - Second: Options (optional)
// - Third: Function run trigger (optional)
const job = new Cron("* * * * * *", { maxRuns: 1 }, () => {} );

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

The job will be sceduled to run at next matching time unless you supply option { paused: true }. The new Cron(...) constructor will return a Cron instance, later called job, which have a couple of methods and properties listed below.

Status

job.nextRun( /*optional*/ startFromDate );	// Get a Date object representing the next run.
job.nextRuns(10, /*optional*/ startFromDate ); // Get an array of Dates, containing the next n runs.
job.previousRuns(10, /*optional*/ referenceDate ); // Get an array of Dates, containing previous n scheduled runs.
job.msToNext( /*optional*/ startFromDate ); // Get the milliseconds left until the next execution.
job.currentRun(); 		// Get a Date object showing when the current (or last) run was started.
job.previousRun( ); 		// Get a Date object showing when the previous job was started.

job.match( date ); 		// Check if a Date object or date string matches the cron pattern (true or false).

job.isRunning(); 	// Indicates if the job is scheduled and not paused or killed (true or false).
job.isStopped(); 	// Indicates if the job is permanently stopped using `stop()` (true or false).
job.isBusy(); 		// Indicates if the job is currently busy doing work (true or false).

job.getPattern(); 	// Returns the original pattern string
job.getOnce(); 		// Returns the original run-once date (Date or null)

Control functions

job.trigger();		// Force a trigger instantly
job.pause();		// Pause trigger
job.resume();		// Resume trigger
job.stop();		// Stop the job completely. It is not possible to resume after this.
				// Note that this also removes named jobs from the exported `scheduledJobs` array.

Properties

job.name 			// Optional job name, populated if a name were passed to options

Options

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

Croner uses Vixie Cron based expressions with the following powerful extensions:

// ┌──────────────── (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)
// │ │ │ │ │ │ ┌──── (optional) year (1 - 9999)
// │ │ │ │ │ │ │
// * * * * * * *

• Optional second and year fields for enhanced precision:

  • 6-field format: SECOND MINUTE HOUR DAY-OF-MONTH MONTH DAY-OF-WEEK
  • 7-field format: SECOND MINUTE HOUR DAY-OF-MONTH MONTH DAY-OF-WEEK YEAR
  • Supported year range: 1-9999

• Advanced calendar modifiers:

  • L: Last day of month or last occurrence of a weekday. L in day-of-month = last day of month; 5#L or FRI#L = last Friday of the month.
  • W: Nearest weekday. 15W triggers on the weekday closest to the 15th (moves to Friday if 15th is Saturday, Monday if 15th is Sunday). Won't cross month boundaries.
  • #: Nth occurrence of a weekday. 5#2 = second Friday; MON#1 = first Monday of the month.

• Enhanced logical control:

  • +: Explicit AND logic modifier. Prefix the day-of-week field with + to require both day-of-month AND day-of-week to match. Example: 0 12 1 * +MON only triggers when the 1st is also a Monday.
  • ?: Wildcard alias (behaves identically to *). Non-portable: Its use is discouraged in patterns intended for cross-system use. Supported in all fields for compatibility, but primarily meaningful in day-of-month and day-of-week fields.
  • Proper DST handling: Jobs scheduled during DST gaps are skipped; jobs in DST overlaps run once at first occurrence.

• 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).

• By default, Croner uses OR logic for day-of-month and day-of-week. Example: 0 20 1 * MON triggers on the 1st of the month OR on Mondays. Use the + modifier (0 20 1 * +MON) or { domAndDow: true } for AND logic. For more information, see issue #53.

Note
Weekday and month names are case-insensitive. Both MON and mon work.
When using L in the Day of Week field with a range, it affects all specified weekdays. For example, 5-6#L means the last Friday and Saturday in the month.
The # character specifies the "nth" weekday of the month. For example, 5#2 = second Friday, MON#1 = first Monday.
The W character operates within the current month and won't cross month boundaries. If the 1st is a Saturday, 1W matches Monday the 3rd.
The + modifier (OCPS 1.4) enforces AND logic: 0 12 1 * +MON only runs when the 1st is also a Monday.
Quartz mode: Enable alternativeWeekdays: true to use Quartz-style weekday numbering (1=Sunday, 2=Monday, ..., 7=Saturday) instead of the standard format (0=Sunday, 1=Monday, ..., 6=Saturday). This is useful for compatibility with Quartz cron expressions.

Predefined schedule nicknames are supported:

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.

For example, some popular alternatives include large datetime libraries as dependencies, which significantly increases bundle size. Croner has zero dependencies and a much smaller footprint, making it ideal for applications where bundle size matters.

In depth comparison of various libraries

	croner	cronosjs	node-cron	cron	node-schedule
Size
Minified size (KB)	22.7	14.9	20.1	93.7	107.8
Bundlephobia minzip (KB)	6.8	5.1	6.1	28.2	31.2
Dependencies	0	0	1	1	3
Popularity
Downloads/week [^1]	2019K	31K	447K	1366K	1046K
Quality
Issues [^1]	0	2	133	13	145
Code coverage	99%	98%	100%	81%	94%
Performance
Ops/s 1 2 3 4 5 6	160 651	55 593	N/A	6 313	2 726
Ops/s 0 0 0 29 2 *	176 714	67 920	N/A	3 104	737
Tests	11/11	10/11	0/11 [^4]	7/11	9/11

Note

• Table last updated at 2023-10-10
• 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

[^1]: As of 2023-10-10
[^2]: Requires support for L-modifier
[^3]: In dom-AND-dow mode, only supported by croner at the moment.
[^4]: Node-cron has no way of showing next run time.

Development

Master branch

This branch contains the latest stable code, released on npm's default channel latest. You can install the latest stable revision by running the command below.

npm install croner --save

Dev branch

This branch contains code currently being tested, and is released at channel dev on npm. You can install the latest revision of the development branch by running the command below.

npm install croner@dev

Warning
Expect breaking changes if you do not pin to a specific version.

A list of fixes and features currently released in the dev branch is available here

Contributing & Support

Croner is founded and actively maintained by Hexagon. If you find value in Croner and want to contribute:

• Code Contributions: See our Contribution Guide for details on how to contribute code.

• Sponsorship and Donations: See github.com/sponsors/hexagon

Your trust, support, and contributions drive the project. Every bit, irrespective of its size, is deeply appreciated.

License

MIT License