Hybrid Styles - Code Like This

Slides

JavaScript is a hybrid language. It has some features from each of these three programming styles:

The overlap between these three can be messy :-(

first-class functions which may be used as parameters and values by other functions
closures to share state between certain functions
- with strict lexical scoping rules (to avoid combinatorial complexity of globals)
immutable data structures, to minimize side effects and maximize concurrency
chaining and iterators and collection pipelines

instance variables (aka properties) as mutable state that survives a single function call
methods to attach functions to an instance
a constructor to initialize your instance with valid values
privacy (aka encapsulation or data hiding) so the instance variables are shared only among the instance methods

Style	Behavior	Local State	Shared State
procedural	functions	variables	globals
functional	functions	variables	nested scope
object-oriented	methods, classes	variables	properties, static methods, class definitions

Note that:

Local state is the same for all styles! Parameters and local variables work the same no matter what.
Methods and closures are each "function plus state"; they differ in where that extra state is stored:
- methods use state inside an object as properties
- closures use state in nested scopes of enclosing functions

All of these styles exist to make code more readable / maintainable / debuggable for humans...

...to the CPU, it's all just ones and zeros.