23. ReactContext

React Context

: pass through App -> Sidebar + ( Dashboard -> AddComment)

1. Provider: Owner
2. Consumer(s)
   • share the parent
   • a subtree of the provider

• argument = null => inaccessible to the provider

• value = {42} => give the value to the CurrentUserContext.Provider, give access

• { value => } => give CurrentUserContext.Provider a Function

–> Modify

Hooks

1. Classes
2. Reuse stateful logic is hard
3. Logic spread into lifecycle methods

Only call hooks at/from…

• the top level
• function components or custom hooks

Function Components

• function name with ‘use’

• useState()

setCounter(counter+1) => (update): counter = counter+1

• useEffect()

• useEffect without [] (initializing) => call setInterval exponentially (setInterval itself calls the function exponentially, it’s like ex*ex)

• useContext()