cron.js

a javascript job scheduler inspired by cron.

• Homepage: http://stefanliebenberg.github.com/cron.js/
• Contact: siga.fredo@gmail.com
• License: http://creativecommons.org/licenses/by/3.0/

notice:

This documentations is incomplete, send me a message on github if you have any questions. Also see the examples folder for some usage examples.

About

cron.js is a cron scheduler for JavaScript. It allows you to run jobs at set intervals, defined by standard cron syntax.

Getting the code:

Grab one of the files in this directory:

https://github.com/StefanLiebenberg/cron.js/tree/master/build

These files should be there:

• cron.compiled.js - compiled with closure. Recommended.
• cron.min.js - minified source code + required closure functions.
• cron.src.js - unminified source code + required closure functions.

Makefile script:

This project uses a makefile to build the required scripts. The following tasks are usefull:

Create the cron.compiled.js file:

make buid/cron.compiled.js

Create the cron.min.js file:

make build/cron.min.js

Create the cron.src.js file:

make build/cron.src.js

Usage:

Usage is inteded to basic. There are three main objects: Cron, Cron.Job, Cron.Spec;

• Cron - Job Scheduler. Manages cron jobs.
• Cron.Job - Cron Job. Contains a schedule and block information for each job.
• Cron.Spec - Cron Specification. Inteprets cron-syntax and contains the logic for calculating date intervals, etc.

###Cron

var cron = new Cron();
cron.start();
cron.add( cronjob );

###Cron.Spec

var spec = new Cron.Spec( '0 0 * * * mon-wed' ) // every minute hour from monday to wednesday;

###Cron.Job

var cronjob = new Cron.Job(new Cron.Spec( '*/10 * * * * *' ), function () {
  console.log('running job');
});

/**
  * @param {string|Cron.Spec} spec spec can be a Cron.Spec object or just a plain string.
  * @param {Function} block block must be a function.
  */
Cron.Job( spec, block );

Syntax:

The general syntax for cron.js looks like this:

// Sec Min Hour Day Month Weekday  
// *  *    *    *   *     *        

There are six columns to a cron schedule: seconds, minutes, hours, days, months, weekdays. You specify specific values for each of these columns so that scheduler can calculate when to run a given job.

For each column, the values could be specific numbers, ranges, intervals or all of these combined in a list.

Specific Numbers:

Each field has different numbers that are allowed, for example seconds and minutes will accept any number between 0 and 59. Whereas hours will only accept numbers between 0-23;

• seconds : 0 to 59
• minutes : 0 to 59
• hours : 0 to 23
• days : 1 to 31
• months : 1 to 12 ( jan, feb, mar and so forth are also supported )
• weekdays : 1 to 7 ( mon, tue, wed, thu and so forth are also supported )

Ranges

Ranges are two numbers seperated with a "-", and they indicate all numbers from one to the other. eg. 10-30 would indicated all numbers between and including 10 to 30.

Interval

A interval is a range and a number seperated by "/". The range specifies the group of values, and number speciefies every nth value to take from that range.
eg. 0-10/2 would indicate every 2nd number from 0 to 10, therefore [0,2,4,6,8,10]

Lists

Lists are either ranges, numbers, or intervals seperated by commas. eg. 10-30,23,30-40/2;

You should combind these six columns to specify a interval at which a job object is to be run:

var schedule = "0 0 0 * * 2-6"; // 00:00:00 on every weeday
new Cron.Job( schedule, function () {
  // do stuff here
});