cron-builder

The software utility cron is a time-based scheduler in Unix-like computer operating systems. A user may use cron to schedule jobs (commands or scripts) to run periodically at fixed times, dates, or intervals. A cron statement is composed of 5 fields separated by white space. The * character translates to "every", ie: "every minute" or "every day of the week".

cron-builder will manage the state of a cron expression, allowing a user to manipulate it through a simple API. It is decoupled from the DOM and doesn't have an opinion about where it's being called from. cron-builder considers this article its source of truth.

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cron-builder is available on npm and bower:
``
npm install cron-builder --save
`
or
`
bower install cron-builder --save
`

After installing, just require the package as you normally would:
`
var cb = require('/path/to/cron-builder.js');
`

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To instantiate the cron builder:

`JavaScript
// (default expression is set to " *")
var cronExp = new cb();

// optionally, pass in a cron expression to override the default:
var myCronExp = new cb('5 12 1-5')
`

To return the cron expression at any given time:
`JavaScript
cronExp.build();
// ' *'
`

API includes basic getters and setters:
`JavaScript
cronExp.get('minute');
// '*'
cronExp.set('minute', '5,35');
// '5,35'
cronExp.get('minute');
// '5,35'
cronExp.build();
// '5,35 '
`

Or if you'd prefer to add or remove values one at a time, use addValue and removeValue. These methods build or take away from what is currently set:
`JavaScript
cronExp.addValue('hour', '2');
cronExp.addValue('monthOfTheYear', '4');
cronExp.addValue('monthOfTheYear', '10');
cronExp.build();
// '5,35 2 4,10 '

cronExp.removeValue('minute', '5');
cronExp.build();
// '35 2 4,10 '
`

If you prefer to work with the expression object directly, use getAll and setAll:
`JavaScript
var exp = cronExp.getAll();
// {minute: ['35'], hour: ['2'], dayOfTheMonth: ['*'], monthOfTheYear: ['4','10'], ...}
exp.dayOfTheMonth = ['7','14','21','28'];
cronExp.setAll(exp);
cronExp.build();
// '35 2 7,14,21,28 4,10 *'
`

##### Notes:
- cron-builder does not currently support using / syntax to indicate values that are repeated. Instead of using */15, use the verbose form 0,15,30,45.
- cron-builder requires using numeric representations of days of the week and months of the year. So instead of using Feb,Mar,Apr just use 2,3,4.

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Easy!
`
npm install
npm test
``
Pull requests and issues appreciated!

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- more validation for things like adding values that are already included in a range, better range validations...
- sorting of values for a given measure of time

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The MIT License (MIT)