Prerequisite Reducer Concepts

• Should have a signature of , similar to the type of function you would pass to Array.prototype.reduce(reducer, ?initialValue)
• Should be "pure", which means the reducer:
  • Does not perform side effects (such as calling API's or modifying non-local objects or variables).
  • Does not call non-pure functions (like Date.now or ).
  • Does not mutate its arguments. If the reducer updates state, it should not modify the existing state object in-place. Instead, it should generate a new object containing the necessary changes. The same approach should be used for any sub-objects within state that the reducer updates.

Because of these rules, it's important that the following core concepts are fully understood before moving on to other specific techniques for organizing Redux reducers:

Redux Reducer Basics

Key concepts:

• Thinking in terms of state and state shape
• Delegating update responsibility by slice of state (reducer composition)
• Higher order reducers

• Redux Docs: Reducers

• Redux Docs: combineReducers
• Stack Overflow: Store initial state and

Pure Functions and Side Effects

Key Concepts:

• Side effects
• Pure functions

• How to think in terms of combining functions
  Reading List:

• Understanding Programmatic Side-Effects
• An Introduction to Reasonably Pure Functional Programming

Immutable Data Management

• Mutability vs immutability
• Immutably updating objects and arrays safely

• Avoiding functions and statements that mutate state
  Reading List:

• Pros and Cons of Using Immutability With React

• Redux Docs: Using the Object Spread Operator

Normalizing Data

Key Concepts:

• Database structure and organization
• Splitting relational/nested data up into separate tables
• Storing a single definition for a given item
• Referring to items by IDs
• Using objects keyed by item IDs as lookup tables, and arrays of IDs to track ordering

• Associating items in relationships
  Reading List:

• Idiomatic Redux: Normalizing the State Shape
• Redux Without Profanity: Normalizr
• Wikipedia: Associative Entity
• Avoiding Accidental Complexity When Structuring Your App State