Mock Stock Ticker

Functional Programming Intro

I got my first introduction to Functional Programming (FP) recently and learned of Kyle Simpson’s wonderful book Functional-Light JS. I thoroughly enjoyed the book not least because of his pragmatic approach to learning FP:

The better I am at writing in a clear, consistent voice, the better this book experience will be for you. But I’m not a 100% perfect author. Some parts will be better written than others. The parts where I can still improve are not going to invalidate the other parts of this book which are useful.

And so it goes with our code. The more you can apply these principles to more parts of your code, the better your code will be. Use them well 25% of the time, and you’ll get some good benefit. Use them 80% of the time, and you’ll see even more benefit.

I look forward to the impact that FP ideas will have on the quality and readability of my coding. And though it may not happen right away, I would love to get more academic about studying FP because it’s just so exciting!

The Project

The core of this is taken from an exercise at the end of Functional-Light JS to build a mock stock ticker using the FP ideas introduced in the book which are manifold: partial application of arguments, currying, composing, piping, mapping, filtering, reducing, and more.

The addition I’ve made is to visualize the stock prices progressively using D3.js.

A few tests

No full test coverage here, but I added some tests in jasmine visible at SpecRunner.html for personal practice and to help me reason through some of the code in the core of the project.