Jank? 🐢

Slow / Stuttery UI performance

React is fast

Reconcilliation

areOwnPropsEqual

areStatesEqual

mapStateToProps

areStatePropsEqual

mergeProps

shouldComponentUpdate 

render

reconciliation

commit > react-dom

componentDidUpdate

react-redux

react

Expensive

Point of no return

props

update lifecycle

react-redux

redux

counter

files

store

combineReducers

mapStateToProps

1 Store

👨‍💻

Jank Demo

mapStateToProps is called on EVERY state change

🚨

> {} === {}

selector pattern

abstract store queries

memoized selectors

reselect 🔥

takeaways

avoid reconciliation 🙅‍♂️

mapStateToProps runs on EVERY state change 🔥

mapStateToProps should be FAST 🐇

don't return new references from mapStateToProps 🚫

redux reducers are combined into single object ☝️ 

reselect for success 💯