cron-validate

Cron-validate is a cron-expression validator written in TypeScript. This is a fork with adaptions to validate Lobaro Device Crons The validation options are customizable and cron fields like seconds and years are supported. The fork aims to support all options from the original repo and to amend whats needed for the Lobaro Crons

Lobaro Modifications

• Support Lobaro CRON validations for H,L,W
• Adding /lib to repo and skip release, requires npm run build to update compiled files in /lib

Usage

Basic usage

1import cron from 'cron-validate'
2
3const cronResult = cron('* * * * *')
4if (cronResult.isValid()) {
5  // !cronResult.isError()
6  // valid code
7} else {
8  // error code
9}

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:

1import cron from 'cron-validate'
2
3const cronResult = cron('* * * * *')
4if (cronResult.isValid()) {
5  const validValue = cronResult.getValue()
6
7  // The valid value is a object containing all cron fields
8  console.log(validValue)
9  // In this case, it would be:
10  // { seconds: undefined, minutes: '*', hours: '*', daysOfMonth: '*', months: '*', daysOfWeek: '*', years: undefiend }
11} else {
12  const errorValue = cronResult.getError()
13
14  // The error value contains an array of strings, which represent the cron validation errors.
15  console.log(errorValue) // string[] of error messages
16}

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)
• npm-cron-schedule (see: https://github.com/P4sca1/cron-schedule)

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

1cron('* * * * *', {
2  preset: 'npm-cron-schedule',
3})

Defining and using your own preset

To define your own preset, use this:

1registerOptionPreset('YOUR-PRESET-ID', {
2  presetId: 'YOUR-PRESET-ID',
3  useSeconds: false,
4  useYears: false,
5  useAliases: false, // optional, default to false
6  useBlankDay: false,
7  allowOnlyOneBlankDayField: false,
8  mustHaveBlankDayField: false, // optional, default to false
9  useLastDayOfMonth: false, // optional, default to false
10  useLastDayOfWeek: false, // optional, default to false
11  useNearestWeekday: false, // optional, default to false
12  useNthWeekdayOfMonth: false, // optional, default to false
13  seconds: {
14    minValue: 0,
15    maxValue: 59,
16    lowerLimit: 0, // optional, default to minValue
17    upperLimit: 59, // optional, default to maxValue
18  },
19  minutes: {
20    minValue: 0,
21    maxValue: 59,
22    lowerLimit: 0, // optional, default to minValue
23    upperLimit: 59, // optional, default to maxValue
24  },
25  hours: {
26    minValue: 0,
27    maxValue: 23,
28    lowerLimit: 0, // optional, default to minValue
29    upperLimit: 23, // optional, default to maxValue
30  },
31  daysOfMonth: {
32    minValue: 1,
33    maxValue: 31,
34    lowerLimit: 1, // optional, default to minValue
35    upperLimit: 31, // optional, default to maxValue
36  },
37  months: {
38    minValue: 0,
39    maxValue: 12,
40    lowerLimit: 0, // optional, default to minValue
41    upperLimit: 12, // optional, default to maxValue
42  },
43  daysOfWeek: {
44    minValue: 1,
45    maxValue: 7,
46    lowerLimit: 1, // optional, default to minValue
47    upperLimit: 7, // optional, default to maxValue
48  },
49  years: {
50    minValue: 1970,
51    maxValue: 2099,
52    lowerLimit: 1970, // optional, default to minValue
53    upperLimit: 2099, // optional, default to maxValue
54  },
55})

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
• useAliases: boolean
  • enables aliases for month and daysOfWeek fields (ignores limits for month and daysOfWeek, so be aware of that)
• 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:

1console.log(cron('* * * * * *', {
2  preset: 'default' // second field not supported in default preset
3  override: {
4    useSeconds: true // override preset option
5  }
6}))
7
8console.log(cron('* 10-20 * * * *', {
9  preset: 'default'
10  override: {
11    minutes: {
12      lowerLimit: 10, // override preset option
13      upperLimit: 20 // override preset option
14    }
15  }
16}))

Examples

1import cron from 'cron-validate'
2
3console.log(cron('* * * * *').isValid()) // true
4
5console.log(cron('* * * * *').isError()) // false
6
7console.log(cron('* 2,3,4 * * *').isValid()) // true
8
9console.log(cron('0 */2 */5 * *').isValid()) // true
10
11console.log(cron('* * * * * *', { override: { useSeconds: true } }).isValid()) // true
12
13console.log(cron('* * * * * *', { override: { useYears: true } }).isValid()) // true
14
15console.log(
16  cron('30 * * * * *', {
17    override: {
18      useSeconds: true,
19      seconds: {
20        lowerLimit: 20,
21        upperLimit: 40,
22      },
23    },
24  }).isValid()
25) // true
26
27console.log(
28  cron('* 3 * * *', {
29    override: {
30      hours: {
31        lowerLimit: 0,
32        upperLimit: 2,
33      },
34    },
35  }).isValid()
36) // false
37
38console.log(
39  cron('* * ? * *', {
40    override: {
41      useBlankDay: true,
42    },
43  }).isValid()
44) // true
45
46console.log(
47  cron('* * ? * ?', {
48    override: {
49      useBlankDay: true,
50      allowOnlyOneBlankDayField: true,
51    },
52  }).isValid()
53) // 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.

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Contributors

• Airfooox
• GuillaumeRochat

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Used by:

• Bree - Job Scheduler For NodeJS

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