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Cron Background

Cron Background is a functional library to parse and generate cron expressions in the UNIX an Quartz formats. Instead of throwing errors, this library returns undefined when the input is invalid. It’s also strictly typed to make it easy to avoid errors when using it.


This one started as a work requirement. When looking for tools to parse CRON expressions, the options out there where mainly class based, and not as strictly typed as I would like. Because of this, I decided to create my own library.


I built this library using TypeScript, with configurations from my shared configs. I made it ESM only as soon as Node started supporting ESM modules, and I made it tree-shakeable by using named exports.

The whole goal was to keep every function in this as atomic as possible, doing only one thing and doing it well. This makes it easier to test and to compose with other functions.

The tests are done with my test library, keeping it pretty simple and with high coverage.


I didn’t used this library much on my own projects, but at work is still being heavily used, and based on the downloads I got before changing the namespace of my projects, looks like there were other folks making use of it as well.