README.md

cron-fns

A simple, zero dependency implementation of cron schedule functions. Runs in the browser, in Node.js, in Deno, anywhere with setTimeout.

Quick Start

npm install cron-fns --save
# or with yarn
yarn add cron-fns

Usage

CronDaemon

Executes a callback on a given schedule.

Note: This should be stopped if no longer in use in the application

import { CronDaemon } from "cron-fns";

const daemon = new CronDaemon("0,30 9-17 * * MON", () => {
  console.log("do some work");
});

// Check when it's going to run next
console.log(daemon.next());

// Stop the daemon
daemon.stop();

// Start it again
daemon.start();

// Check if it's running
console.log(daemon.state()); // "running"

nextCronOccurrence(schedule, from?) => Date | undefined

Fetches the next date that matches the schedule, or undefined if no other time is available.

import { nextCronOccurrence } from "cron-fns";

nextCronOccurrence("0,30 9-17 * * MON", new Date("2020-01-01T00:00:00"));
// Returns 2020-01-06T09:00:00

// `from` defaults to the current date if not specified.
nextCronOccurrence("0,30 9-17 * * MON 1987");
// Returns undefined if no more possible dates

nextCronOccurrences(schedule, from?)

Returns a generator which iterates through each sequential date in order from the specified start point. The generator will only stop iterating if there is no more possible dates.

import { nextCronOccurrences } from "cron-fns";

nextCronOccurrences("0,30 9-10 * * MON", new Date("2020-01-01T00:00:00"));
// Returns a generator with the sequence:
// 2020-01-06T09:00:00
// 2020-01-06T09:30:00
// 2020-01-06T10:00:00
// ...

Cron

import { Cron } from "cron-fns";
const cron = new Cron("0,30 9-17 * * MON");
cron.next(); // Returns the next date from now
cron.next(new Date("2020-01-01T00:00:00")); // Returns 2020-01-06T09:00:00

Cron syntax rules

//                    ┌───────────── minute (0 - 59)
//                    │    ┌───────────── hour (0 - 23)
//                    │    │  ┌───────────── day of the month (1 - 31)
//                    │    │  │ ┌───────────── month (1 - 12)
//                    │    │  │ │  ┌───────────── day of the week (0 - 6) (Sunday to Saturday)
//                    │    │  │ │  │
//                    │    │  │ │  │
nextCronOccurrence("0,30 9-17 * * MON");

• Use a single space to separate fields.
• Enumerate multiple values for a field by separating by a comma (,).
• Specify a range of values with a hyphen (-).
• Ranges and enumeration cannot be mixed.

Cron variations & notes

Optional years

If you specify 6 fields then the last field is the year. If not specifed it doesn't limit by year.

Optional seconds

If you specify 7 fields then the first field is the second. If not specified it chooses the zeroth second of each minute.

Timezones

All times and dates are based on the system (or browser's) local timezone.