recurrence

Calculates the diff between dates and returns a nicely formatted string.

Turns an array of dates into:

• every 4 days
• monthly
• every 10 hours
• etc

Installation

npm install --save recurrence

Usage

const recurrence = require('recurrence');

const dates = [
  new Date(2016, 1, 1),
  new Date(2016, 1, 2)
  new Date(2016, 1, 3)
];

console.log(recurrence(dates));

Duplicate dates are removed and the order doesn't matter.

Output

{
  "count": 1,
  "unit": "day/week/month/year",
  "recurrence": "Daily"
}

In the output recurrence is set to something that you could show directly to a user.

Values look like this:

• every 5 seconds
• every 30 minutes
• hourly
• every 8 hours
• daily
• every 3 weeks
• monthly
• yearly
• every 10 years

Of course you can use the count and unit for your own output, maybe for other languages or otherwise different results.

Options

You can pass an options object as the second argument.

Defaults:

{
  "numberAsString": false,
  "strict": false,
  "noSingleUnits": false
}

Override any of these by passing in an object:

recurrence(dates, {
  strict: true,
  numberAsString: true
});

numberAsString

Outputs the number as a text:

• true: 'Every four years'
• false: 'Every 4 years'

strict

Throw an exception if an invalid date is detected. With strict = false just ignores the date.

noSingleUnits

Doesn't format strings as daily or yearly so it returns Every second/hour/month/year etc instead of daily or weekly

Example

const recurrence = require('recurrence');

const leapyears = [
  new Date(2016, 1, 29),
  new Date(2012, 1, 29)
  new Date(2008, 1, 29)
];

const result = recurrence(leapyears, {
  numberAsString: true  
});

console.log(`Leap year happens ${result.recurrence}!`);
// Leap year happens every four years!

Test

npm run test

Coverage

npm run cover