Structuring logic.
WHAT A FUNCTION IS
A named block of code, taking inputs and returning a result.
WHAT MAKES A GOOD ONE
It does one thing Its name says what It is short It does not depend on hidden state
WHAT TO DECLARE
The types it accepts and returns.
WHY
It documents intent and catches mistakes early.
WHAT TO AVOID
Functions with many parameters Functions modifying things outside themselves Global variables
WHY GLOBALS CAUSE PROBLEMS
Anything can change them, so nothing can be reasoned about.
WHAT TO USE INSTEAD
Parameters and return values Objects holding their own state
WHAT CLASSES PROVIDE
Grouping data with the operations on it.
WHEN TO USE ONE
When data and behaviour belong together When you need several instances of something
WHAT NAMESPACES DO
Prevent name collisions between your code and libraries.
WHAT TO ADOPT
A conventional structure where file paths match class names, so loading is automatic.
