cron-parser

Node.js library for parsing and manipulating crontab instructions. It includes support for timezones and DST transitions.

Compatibility
Node >= 0.8
Typescript <= 4.2

Setup

npm install cron-parser

Supported format

*    *    *    *    *    *
┬    ┬    ┬    ┬    ┬    ┬
│    │    │    │    │    |
│    │    │    │    │    └ day of week (0 - 7) (0 or 7 is Sun)
│    │    │    │    └───── month (1 - 12)
│    │    │    └────────── day of month (1 - 31, L)
│    │    └─────────────── hour (0 - 23)
│    └──────────────────── minute (0 - 59)
└───────────────────────── second (0 - 59, optional)

Supports mixed use of ranges and range increments (L and W characters are not supported currently). See tests for examples.

Usage

Simple expression.

var parser = require('cron-parser');

try {
  var interval = parser.parseExpression('*/2 * * * *');

  console.log('Date: ', interval.next().toString()); // Sat Dec 29 2012 00:42:00 GMT+0200 (EET)
  console.log('Date: ', interval.next().toString()); // Sat Dec 29 2012 00:44:00 GMT+0200 (EET)

  console.log('Date: ', interval.prev().toString()); // Sat Dec 29 2012 00:42:00 GMT+0200 (EET)
  console.log('Date: ', interval.prev().toString()); // Sat Dec 29 2012 00:40:00 GMT+0200 (EET)
} catch (err) {
  console.log('Error: ' + err.message);
}

Iteration with limited timespan. Also returns ES6 compatible iterator (when iterator flag is set to true).

var parser = require('cron-parser');

var options = {
  currentDate: new Date('Wed, 26 Dec 2012 12:38:53 UTC'),
  endDate: new Date('Wed, 26 Dec 2012 14:40:00 UTC'),
  iterator: true
};

try {
  var interval = parser.parseExpression('*/22 * * * *', options);

  while (true) {
    try {
      var obj = interval.next();
      console.log('value:', obj.value.toString(), 'done:', obj.done);
    } catch (e) {
      break;
    }
  }

  // value: Wed Dec 26 2012 14:44:00 GMT+0200 (EET) done: false
  // value: Wed Dec 26 2012 15:00:00 GMT+0200 (EET) done: false
  // value: Wed Dec 26 2012 15:22:00 GMT+0200 (EET) done: false
  // value: Wed Dec 26 2012 15:44:00 GMT+0200 (EET) done: false
  // value: Wed Dec 26 2012 16:00:00 GMT+0200 (EET) done: false
  // value: Wed Dec 26 2012 16:22:00 GMT+0200 (EET) done: true
} catch (err) {
  console.log('Error: ' + err.message);
}

Timezone support

var parser = require('cron-parser');

var options = {
  currentDate: '2016-03-27 00:00:01',
  tz: 'Europe/Athens'
};

try {
  var interval = parser.parseExpression('0 * * * *', options);

  console.log('Date: ', interval.next().toString()); // Date:  Sun Mar 27 2016 01:00:00 GMT+0200
  console.log('Date: ', interval.next().toString()); // Date:  Sun Mar 27 2016 02:00:00 GMT+0200
  console.log('Date: ', interval.next().toString()); // Date:  Sun Mar 27 2016 04:00:00 GMT+0300 (Notice DST transition)
} catch (err) {
  console.log('Error: ' + err.message);
}

Manipulation

var parser = require('cron-parser');

var interval = parser.parseExpression('0 7 * * 0-4');
var fields = JSON.parse(JSON.stringify(interval.fields)); // Fields is immutable
fields.hour = [8];
fields.minute = [29];
fields.dayOfWeek = [1,3,4,5,6,7];
var modifiedInterval = parser.fieldsToExpression(fields);
var cronString = modifiedInterval.stringify();
console.log(cronString); // "29 8 * * 1,3-7"

Options

• currentDate - Start date of the iteration
• endDate - End date of the iteration

currentDate and endDate accept string, integer and Date as input.

In case of using string as input, not every string format accepted by the Date constructor will work correctly. The supported formats are: ISO8601 and the older ASP.NET JSON Date format. The reason being that those are the formats accepted by the moment library which is being used to handle dates.

Using Date as an input can be problematic specially when using the tz option. The issue being that, when creating a new Date object without any timezone information, it will be created in the timezone of the system that is running the code. This (most of times) won't be what the user will be expecting. Using one of the supported string formats will solve the issue(see timezone example).

• iterator - Return ES6 compatible iterator object
• utc - Enable UTC
• tz - Timezone string. It won't be used in case utc is enabled