https://github.com/bsdelf/recron
Simple, intuitive and readable cron implementaiton
https://github.com/bsdelf/recron
cron cronjob crontab interval periodic timer timezone typescript
Last synced: about 2 months ago
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Simple, intuitive and readable cron implementaiton
- Host: GitHub
- URL: https://github.com/bsdelf/recron
- Owner: bsdelf
- License: mit
- Created: 2019-10-30T02:38:44.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2025-03-03T10:56:29.000Z (4 months ago)
- Last Synced: 2025-03-30T14:22:08.110Z (3 months ago)
- Topics: cron, cronjob, crontab, interval, periodic, timer, timezone, typescript
- Language: TypeScript
- Homepage:
- Size: 489 KB
- Stars: 6
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Recron
Recron is a simple, intuitive and readable cron implementaiton written in TypeScript and suitable for Node.js and browser usage.
## Highlights
- Object oriented design.
- Support update schedule on the fly.
- Support both crontab and interval syntax.
- Support different time zones in a single cron instance.
- Tickless scheduler (will be optional in future).
- Compact and quite readable code base written in TypeScript.
## Usage
```typescript
import { Cron } from 'recron';
const cron = new Cron();
// Start cron scheduler.
cron.start();
// Use interval syntax.
cron.schedule('@every 1s', () => {
console.log('every second', new Date());
});
// Use crontab syntax.
cron.schedule('*/5 * * * * *', () => {
console.log('at 5th second', new Date());
});
// Stop cron after 10 seconds.
cron.schedule(
'@every 10s',
() => {
cron.stop();
console.log('done', new Date());
},
{ oneshot: true }
);
```
## Time zone
The constructor of `Cron` has an optional parameter to let you set time zone.
If the `timezone` parameter is unspecified, the default time zone will be detected from [`Intl.DateTimeFormat`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DateTimeFormat/resolvedOptions), it will be your local time zone in general.
Also, the last parameter of `schedule()` method `options` has an optional `timezone` property,
which can be used to override the default time zone for individual schedule.
Note: time zone only affects crontab, it does not affect the interval usage.
## Reentrant
Unlike other cron implementations,
reentrant is not allowd in `recron` by default for both safety and convenient.
Therefore, if the scheduled callback function takes a lot of time to process, it will underrun.
For example, given following piece of code:
```typescript
const sleep = (ms: number) => new Promise((resolve) => setTimeout(resolve, ms));
cron.schedule('@every 1s', async () => {
console.log('overslept', new Date());
await sleep(3000);
});
```
the output will be:
```
overslept 2019-10-31T05:05:27.251Z
overslept 2019-10-31T05:05:30.253Z
overslept 2019-10-31T05:05:34.254Z
overslept 2019-10-31T05:05:37.263Z
overslept 2019-10-31T05:05:40.275Z
```
To disable this feature, set `reentrant` to `true` in options.
But be careful, if the providered callback function keeps underrun,
due to the unresolved promises,
the memory consumption will be increasing,
and eventually you program will run out-of-memory.
## Crontab Alias
`recron` has following crontab aliases:
| Alias | Crontab |
| -------- | ------------- |
| @hourly | 0 \* \* \* \* |
| @daily | 0 0 \* \* \* |
| @weekly | 0 0 \* \* 1 |
| @monthly | 0 0 1 \* \* |
Note: we regard Monday as the first day of the week according to international standard ISO 8601. So `@weekly` means "at 00:00 on Monday", not Sunday.
## Interval Syntax
Interval syntax has following specifiers:
| Order | Specifier | Unit |
| ----- | --------- | ----------- |
| 1 | h | hour |
| 2 | m | minute |
| 3 | s | second |
| 4 | ms | Millisecond |
One ore more specifiers can be used, as long as they are arranged in ascending order:
- `@every 10s`
- `@every 30m`
- `@every 1h30m`