React Hooks useContext and useReducer

Question 1

What must you create before using the useContext hook?

Accepted Answer

A context object with React.createContext

Answer

React.createContext creates the context object that holds the value passed down through the component tree.

Question 2

What does the useContext hook return?

Accepted Answer

The nearest Provider's value prop

Answer

useContext returns the current value from the nearest matching Context.Provider above the component.

Question 3

When does a component using useContext re-render?

Accepted Answer

When the Provider's value prop changes

Answer

React re-renders all consumers whenever the Provider's value reference changes.

Question 4

What is the first argument to useReducer?

Accepted Answer

A reducer function (state, action) => newState

Answer

useReducer takes a reducer function that receives the current state and an action, then returns the new state.

Question 5

What does useReducer return?

Accepted Answer

A [state, dispatch] tuple

Answer

useReducer returns a [state, dispatch] pair, where dispatch sends actions to the reducer.

React Practice Test