redux-intro
The State Problem
Applications are becoming more complex
GUI applications have many different points of interaction, leading to different sources of state updates
Web applications have to reconcile state between client and server
Asynchronous nature of JavaScript and server-side calls introduces additional points of failure
Server side rendering, caching, and distributed data add more complexity
What is Redux
Redux is a predictable state container for JavaScript apps.
A framework for managing state
Streamlines state interactions using a common pattern
Removes two-way interaction in favor of a uni-directional data flow
Three Principles
A single source of truth
State is read-only
State is updated using pure functions
How Redux Works
![Redux Flow]()
Actions
The sole mechanism for inducing changes in state
Application dispatches actions whenever an event happens
E.g., button clicked, page has finished loading, AJAX call has returned data
Actions contain:
Something that identifies the change
Any additional information needed to update the state
Reducer
The method by which state is actually changed
Takes the "before" state and the action and returns the "after" state
Follows the same data flow as the general programming concept of a "reducer"
Store
Where the entire application state exists
An application should only have one store
In larger applications, the store will have several parts
Partitioning state is a key architectural decision
Getting Redux
Redux is available via NPM
npm install redux
There is also a package that provides easy interoperability between Redux and React called
react-reduxnpm install react-reduxMakes integration easier but is not absolutely necessary
Redux DevTools
Visualize your application's current state
Move forward and backwards throughout your state (time travelling!)
Available for Chrome, Firefox and Electron and other environments
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