typescript 中的 useContext 和 useReducer

Question

I'm new to typescript and I was implementing react useContext and useReducer. I was following a tutorial but im getting an error of Parameter 'action' implicitly has an 'any' type. In my reducer function.

reducer function

function reducer(state, action) { // error Parameter 'action' implicitly has an 'any' type.
     return { count: state.count + 1 }
}

CountProvider

   const [state, dispatch] = useReducer(reducer, {
    count: 0
   })

Answer 1

You have to specify the type of action as any or do it by generic form. In case you want to structure action you could create an interface.

function reducer(state, action: { [key: string]: string|number }) { // error Parameter 'action' implicitly has an 'any' type.
    return { count: state.count + 1 }
}