cron-validate

What is cron-validate?

The cron-validate npm package is used to validate and parse cron expressions. It ensures that cron expressions are syntactically correct and can be used to schedule tasks in a reliable manner.

What are cron-validate's main functionalities?

Basic Validation

This feature allows you to validate a basic cron expression. The code sample checks if the cron expression '0 0 * * *' is valid.

const cronValidate = require('cron-validate');
const result = cronValidate('0 0 * * *');
console.log(result.isValid()); // true

Custom Validation Options

This feature allows you to validate a cron expression with custom options. The code sample uses a preset option to validate the cron expression.

const cronValidate = require('cron-validate');
const options = { preset: 'npm-package' };
const result = cronValidate('0 0 * * *', options);
console.log(result.isValid()); // true

Detailed Error Messages

This feature provides detailed error messages for invalid cron expressions. The code sample demonstrates how to get an error message for an invalid cron expression.

const cronValidate = require('cron-validate');
const result = cronValidate('invalid-cron');
console.log(result.getError()); // Detailed error message

Other packages similar to cron-validate

cron-parser

The cron-parser package is used to parse and manipulate cron expressions. It provides similar validation capabilities but also includes features for parsing and iterating over cron schedules. Compared to cron-validate, it offers more advanced manipulation of cron expressions.

node-cron

The node-cron package is a task scheduler in pure JavaScript for node.js based on cron syntax. While it includes validation of cron expressions, its primary focus is on scheduling tasks rather than just validation. It is more feature-rich in terms of task scheduling compared to cron-validate.

cron

The cron package is another task scheduler for node.js that uses cron syntax. It includes validation as part of its scheduling capabilities. Similar to node-cron, it is more focused on task scheduling and execution rather than just validation.

README

cron-validate

Cron-validate is a cron-expression validator written in TypeScript. The validation options are customizable and cron fields like seconds and years are supported.

Installation

Pacakge is available on npm:

npm install -S cron-validate

Usage

Basic usage

import cron from 'cron-validate'

const cronResult = cron('* * * * *')
if (cronResult.isValid()) {
  // !cronResult.isError()
  // valid code
} else {
  // error code
}

Result system

The cron function returns a Result-type, which is either Valid<T, E> or Err<T, E>.

For checking the returned result, just use result.isValid() or result.isError()

Both result types contain values:

import cron from 'cron-validate'

const cronResult = cron('* * * * *')
if (cronResult.isValid()) {
  const validValue = cronResult.getValue()

  // The valid value is a object containing all cron fields
  console.log(validValue)
  // In this case, it would be:
  // { seconds: undefined, minutes: '*', hours: '*', daysOfMonth: '*', months: '*', daysOfWeek: '*', years: undefiend }
} else {
  const errorValue = cronResult.getError()

  // The error value contains an array of strings, which represent the cron validation errors.
  console.log(errorValue) // string[] of error messages
}

Make sure to test the result type beforehand, because getValue() only works on Valid and getError() only works on Err. If you don't check, it will throw an error.

For further information, you can check out https://github.com/gDelgado14/neverthrow, because I used and modified his code for this package. (Therefor not every documented function on his package is available on this package.)

Options / Configuration

To configure the validator, cron-validate uses a preset system. There are already defined presets (default, npm-node-cron or aws), but you can also define your own preset to use for your system. You can also use the override property to set certain option on single cron validates.

Presets

The following presets are already defined by cron-validate:

• default (see: http://crontab.org/)
• npm-node-cron (see: https://github.com/kelektiv/node-cron)
• aws-cloud-watch (see: https://docs.aws.amazon.com/de_de/AmazonCloudWatch/latest/events/ScheduledEvents.html)

To select a preset for your validation, you can simply do this:

cron('* * * * *', {
  preset: 'npm-node-cron',
})

or

cron('* * * * *', {
  preset: 'aws-cloud-watch',
})

Defining and using your own preset

To define your own preset, use this:

registerOptionPreset('YOUR-PRESET-ID', {
  presetId: 'YOUR-PRESET-ID',
  useSeconds: false,
  useYears: false,
  useBlankDay: false,
  allowOnlyOneBlankDayField: false,
  mustHaveBlankDayField: false, // optional, default to false
  useLastDayOfMonth: false, // optional, default to false
  useLastDayOfWeek: false, // optional, default to false
  seconds: {
    minValue: 0,
    maxValue: 59,
    lowerLimit: 0, // optional, default to minValue
    upperLimit: 59, // optional, default to maxValue
  },
  minutes: {
    minValue: 0,
    maxValue: 59,
    lowerLimit: 0, // optional, default to minValue
    upperLimit: 59, // optional, default to maxValue
  },
  hours: {
    minValue: 0,
    maxValue: 23,
    lowerLimit: 0, // optional, default to minValue
    upperLimit: 23, // optional, default to maxValue
  },
  daysOfMonth: {
    minValue: 1,
    maxValue: 31,
    lowerLimit: 1, // optional, default to minValue
    upperLimit: 31, // optional, default to maxValue
  },
  months: {
    minValue: 0,
    maxValue: 12,
    lowerLimit: 0, // optional, default to minValue
    upperLimit: 12, // optional, default to maxValue
  },
  daysOfWeek: {
    minValue: 1,
    maxValue: 7,
    lowerLimit: 1, // optional, default to minValue
    upperLimit: 7, // optional, default to maxValue
  },
  years: {
    minValue: 1970,
    maxValue: 2099,
    lowerLimit: 1970, // optional, default to minValue
    upperLimit: 2099, // optional, default to maxValue
  },
})

The preset properties explained:

• presetId: string
  • same id as in first function parameter
• useSeconds: boolean
  • enables seconds field in cron expression
• useYears: boolean
  • enables years field in cron expression
• useBlankDay: boolean
  • enables blank day notation '?' in daysOfMonth and daysOfWeek field
• allowOnlyOneBlankDayField: boolean
  • requires a day field to not be blank (so not both day fields can be blank)
• mustHaveBlankDayField: boolean
  • requires a day field to be blank (so not both day fields are specified)
  • when mixed with allowOnlyOneBlankDayField, it means that there will always be either day or day of week as ?
• useLastDayOfMonth: boolean
  • enables the 'L' character to specify the last day of the month.
  • accept negative offset after the 'L' for nth last day of the month.
  • e.g.: L-2 would me the 2nd to last day of the month.
• useLastDayOfWeek: boolean
  • enables the 'L' character to specify the last occurrence of a weekday in a month.
  • e.g.: 5L would mean the last friday of the month.
• useNearestWeekday: boolean
  • enables the 'W' character to specify the use of the closest weekday.
  • e.g.: 15W would mean the weekday (mon-fri) closest to the 15th when the 15th is on sat-sun.
• useNthWeekdayOfMonth: boolean
  • enables the '#' character to specify the Nth weekday of the month.
  • e.g.: 6#3 would mean the 3rd friday of the month (assuming 6 = friday).

• in cron fields (like seconds, minutes etc.):
  • minValue: number
    • minimum value of your cron interpreter (like npm-node-cron only supports 0-6 for weekdays)
    • can't be set as override
  • maxValue: number
    • minimum value of your cron interpreter (like npm-node-cron only supports 0-6 for weekdays)
    • can't be set as override
  • lowerLimit?: number
    • lower limit for validation
    • equal or greater than minValue
    • if not set, default to minValue
  • upperLimit?: number
    • upper limit for validation
    • equal or lower than maxValue
    • if not set, defaults to maxValue

Override preset options

If you want to override a option for single cron validations, you can use the override property:

console.log(cron('* * * * * *', {
  preset: 'default' // second field not supported in default preset
  override: {
    useSeconds: true // override preset option
  }
}))

console.log(cron('* 10-20 * * * *', {
  preset: 'default'
  override: {
    minutes: {
      lowerLimit: 10, // override preset option
      upperLimit: 20 // override preset option
    }
  }
}))

Examples

import cron from 'cron-validate'

console.log(cron('* * * * *').isValid()) // true

console.log(cron('* * * * *').isError()) // false

console.log(cron('* 2,3,4 * * *').isValid()) // true

console.log(cron('0 */2 */5 * *').isValid()) // true

console.log(cron('* * * * * *', { override: { useSeconds: true } }).isValid()) // true

console.log(cron('* * * * * *', { override: { useYears: true } }).isValid()) // true

console.log(
  cron('30 * * * * *', {
    override: {
      useSeconds: true,
      seconds: {
        lowerLimit: 20,
        upperLimit: 40,
      },
    },
  }).isValid()
) // true

console.log(
  cron('* 3 * * *', {
    override: {
      hours: {
        lowerLimit: 0,
        upperLimit: 2,
      },
    },
  }).isValid()
) // false

console.log(
  cron('* * ? * *', {
    override: {
      useBlankDay: true,
    },
  }).isValid()
) // true

console.log(
  cron('* * ? * ?', {
    override: {
      useBlankDay: true,
      allowOnlyOneBlankDayField: true,
    },
  }).isValid()
) // false

(Planned) Features

• Basic cron validation.
• Error messenges with information about invalid cron expression.
• Seconds field support.
• Years field support.
• Option presets (classic cron, node-cron, etc.)
• Blank '?' daysOfMonth/daysOfWeek support
• Last day of month.
• Last specific weekday of month. (e.g. last Tuesday)
• Closest weekday to a specific day of the month.
• Nth specific weekday of month. (e.g. 2nd Tuesday)
• Cron alias support.

---

Contributors

• Airfooox
• GuillaumeRochat

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Used by:

• Bree - Job Scheduler For NodeJS

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Changelog

1.2.0 (2020-07-29)

Bug Fixes

• deps: update dependency yup to v0.29.2 (#87) (cb8cdfe)
• add explicit return types to avoid Result<unknown, ...> (#78) (177e301)

Features

• Extending AWS Preset wildcards and checks. (#80) (a7baca0)