Experimental Naive Lenses

A naive implementation of functional lenses for educational purposes.

These experiments use https://github.com/kutyel/optics.js created by Flavio Corpa. The repo readme includes a very good overview and some accompanying videos.

I'm using https://github.com/apache/drill/blob/master/exec/java-exec/src/test/resources/donuts.json as a sample data set.

Notes on Lenses

WTF is a Lens

A Lens is a function which facilitates working with deeply nested data. It is generally part of a broader Optics package. These are functional design patterns originalting in Scala and Haskell. They can be found in most functional libraries such as Ramda or monocole.ts (which is part of the fp-ts ecosystem).

Like everything else in FP lenses can be composed with other lenses to effectively drill into even more complex data structures.

There are two main parts to a lens optic:

The Lens itself which is a kind of optic that allows us to "focus" on a specific part (often called the subpart) of a deeply nested data object
The Operation which we want to conduct on that particular Lens

Lens Operations

Lenses have only three possible operations.

View (Get) - get the value of a lense
Set - set the value of a lense
Over (Modify) - map over contents applying a function

Build Scripts

yarn dev to go into development mode with live reload
yarn clean to clean the /dist directory
yarn prod to create a distributable bundle in /dist (terses and removes logs)

The Stack