Reading Class 9 - Ginsusamurai/seattle-301d58 GitHub Wiki

concepts of functional programming

functional programming - building around the evaluation of mathematical functions and avoiding changing-state and mutable data
pure functions are deterministic, no observable side effects
external variables NOT passed as arguments can be non-pure as that variable's state can change at execution
reading external files is not pure, those files can be changed
random number generation can not be pure
pure functions do not modify globals or the things they take in as arguments or if they do, just return values from them without assignment
.map() is a pure function since it doesn't alter the original array
recursion can be used for loops to make them pure by keeping variables immutable
memoizing functions can let you pass and stack them around
higher order functions take in functions as an argument
you can pass a func to .filter() if it's formatted right
consistent use of constants and returning back new values/arays preents over-writing and maintains immutable data

hash map a key to a location in the hash table
tbl.set(key, val)
early function returns to see if a bad state (no user) to reduce wasted time
set vars during loops or while other tasks are performed to make code self documenting (avoiding thing.object.way[0].item