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.
• 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), Deno >=1.16 and Bun >=0.2.2.
• Works in browsers as standalone, UMD or ES-module.
• Schedule using specific target time zones.
• Over-run protection with callback
• Built in error handling with callback
• 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.

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

[^1]: As of 2022-10-08 [^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.

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@5.6.4/src/croner.js";

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

TypeScript

import { Cron } from "https://deno.land/x/croner@5.6.4/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

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:

  • ? 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.

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

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

Contributing

Master branch

Dev branch

All development happen in the dev branch, you can install latest development version of croner using

npm install croner@dev

See Contribution Guide

... or ...

License

MIT License