Functional Programming Notes

Actions:
   Anything that depends on when it is run, or how many times it is run, or both, is an action.
Calculations
   Calculations are computations from input to output. They always give the same output when you give them the same input.
Data
   Data is recorded facts about events.
   * Serializable, Compare for equality, Open for interpretation

Notes:
   pp.11 Once computers talk over networks, things get chaotic. Messages arrive out of order, are duplicated, or never arrive at all. Making sense of what happened when, basically modeling change over time, is very important, but also difficult. The more we can do to eliminate a dependency on when or how many times, the easier it will be to avoid serious bugs.
   Data and calculations do not depend on how many times they are run or accessed. By moving more of our code into data and calculations, we sweep that code clean of the problems inherent in distributed systems.

   pp.13  three important ideas are 1) distinguishing actions, calculations, and data, 2) using first-class abstractions, and 3) building composable models.

   pp.62 Ch.4 Extracting calculations from actions

Q: Are reusability and testability the only concerns that functional programming helps with?
A: Absolutely not! FP does help with those, but there’s a lot more out there. We’ll get to concurrency, architecture, and data modeling by the end of the book. Also, FP is a big field and this book cannot cover all of it.

Copy-on-Write
   Make a copy, Modify the copy, Return the copy
   Making copies allows us to keep the original and the copy without worry that it will change. This is great for implementing undo/ redo.

JavaScript Object Copy
var item_copy = Object.assign({}, item);