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

Try it live on jsfiddle.

Croner - Cron for JavaScript and TypeScript

• Trigger functions in JavaScript using Cron syntax.
• Works in Node.js >=7.6 (both require and import), Deno >=1.16 and Bun >=0.2.2.
• Works in browsers as standalone, UMD or ES-module.
• Target different time zones.
• Built in Overrun protection with callback
• Built in error handling with callback
• Includes TypeScript typings.
• 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.
• Uses Vixie-cron pattern, with a few additional features such as L for last day and weekday of month.

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 on?
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.

Installation

If you are migrating from a different library such as cron or node-cron, or upgrading from a older version of croner, see MIGRATION.md.

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@6.0.0-dev.0/dist/croner.js";

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

TypeScript

import { Cron } from "https://deno.land/x/croner@6.0.0-dev.0/dist/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.umd.min.js (UMD and standalone) or croner.min.js (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@6/dist/croner.umd.min.js"></script>

To use as an ES-module

<script type="module">
    import Cron from "https://cdn.jsdelivr.net/npm/croner@6/dist/croner.min.js";

    // ... 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
job.next( /*optional*/ previousRun );	// Get a Date object representing next run
job.enumerate(10, /*optional*/ startFrom ); // Get a array of Dates, containing next n runs according to pattern
job.msToNext( /*optional*/ previousRun ); // Milliseconds left to next execution
job.running(); 		// Scheduler is running (not paused or stopped)
job.busy(); 		// Returns boolean showing if a triggered function is currenly working
job.started(); 		// Date object showing when current (or last) run were started
job.previous( ); 	// Date object showing when previous job were started

// Job control
job.trigger();		// Force a trigger instantly
job.pause();		// Pause trigger
job.resume();		// Resume trigger
job.stop();			// Stop job completely, it isn't possible to resume after this

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

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

// ┌──────────────── (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)
// │ │ │ │ │ │
// * * * * * *

• Croner expressions have the following additional modifiers:

  • ?: The question mark is substituted with the time of initialization. For example, ? ? * * * * would be substituted with 25 8 * * * * if the time is :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. It can also be used in the day of the week field to specify the last specific weekday of the month, for example, the last Friday.

• 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.

Note Weekday and month names are case-insensitive. Both MON and mon work. When using L in the Day of Week field, it affects all specified weekdays. For example, L5,6 means the last Friday and Saturday in the month.”

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

Development

Master branch

This branch contains the latest stable code, released on npm’s default channel (latest).

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

A list of fixes and features currently released in the dev branch (but not in master) is available here

Contributing

See Contribution Guide

… or …

License

MIT License