Croner
Trigger functions in JavaScript using Cron syntax.

Try it live on jsfiddle.

Croner

Trigger functions in JavaScript using Cron syntax.
Pause, resume or stop execution after a task is scheduled.
Find first date of next month, find date of next tuesday, etc.
Works in Node.js >=4.0 (both require and import).
Works in Deno >=1.16.
Works in browsers as standalone, UMD or ES-module.
Experimental feature: Schedule in specific target timezones.
Includes TypeScript typings.

Quick examples:

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

// What date is next sunday?
const nextSunday = Cron('0 0 0 * * 7').next();
console.log(nextSunday.toLocaleDateString());

// How many days left to christmas eve?
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");

More examples…

Installation

Node.js

npm install croner --save

JavaScript

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

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

TypeScript

Note that only default export is available in Node.js TypeScript, as the commonjs module is used internally.

import Cron from "croner";

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

Deno

JavaScript

import Cron from "https://cdn.jsdelivr.net/gh/hexagon/croner@4/src/croner.js";

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

TypeScript

import { Cron } from "https://cdn.jsdelivr.net/gh/hexagon/croner@4/src/croner.js";

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

Browser

Manual

Download latest zipball
Unpack
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@4/dist/croner.min.js"></script>

To use as a ES-module

<script type="module">
    import Cron from "https://cdn.jsdelivr.net/npm/croner@4/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("* * * * * *" , /*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 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
maxRuns	Infinite	Number
catch	false	Boolean	Catch and ignore unhandled errors in triggered function
timezone	undefined	String	Timezone in Europe/Stockholm format
startAt	undefined	String	ISO 8601 formatted datetime (2021-10-17T23:43:00) in local or specified timezone
stopAt	undefined	String	ISO 8601 formatted datetime (2021-10-17T23:43:00) in local or specified timezone
paused	false	Boolean	If the job should be paused from start.
context	undefined	Any	Passed as the second parameter to triggered function

Pattern

// ┌──────────────── (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	* , - /
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 works.

Examples

Expressions

// Run a function according to pattern
Cron('15-45/10 */5 1,2,3 * JAN-MAR SAT', function () {
    console.log('This will run every tenth second between second 15-45');
    console.log('every fifth minute of hour 1,2 and 3');
    console.log('every saturday in January to March.');
});

Find dates

// Find next month
const nextMonth = Cron('0 0 0 1 * *').next(),
    nextSunday = Cron('0 0 0 * * 7').next(),
    nextSat29feb = Cron("0 0 0 29 2 6").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

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 in Europe/Stockholm.');
    }
);

Job controls

const job = Cron('* * * * * *', (self) => {
    console.log('This will run every second. Pause on second 10. Resume on second 15. And quit on second 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();
});

Contributing

See Contribution Guide

License

MIT