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Reputation: 22520

Why do I get 'Expected the reducer to be a function.'?

I am getting my head around redux/react but having issues with my reducer:

const reducer = (state = 0, action) => {
  switch (action.type) {
    case "INCREMENT":
      return state++;

    default:
      return state;
  }
};

Trying to inject this into my store:

const store = createStore(reducer);

How can I avoid this error?

link to codepen

Upvotes: 0

Views: 60

Answers (1)

Joshua R.
Joshua R.

Reputation: 2302

Thanks for the sandbox!

Your "reducer" variable isn't defined when createStore is executed. Either 1) define it before you use it, or 2) define it with a function declaration:

function reducer(state = 0, action) {
  switch (action.type) {
    case "INCREMENT":
      return state++;

    default:
  return state;
  }
}

which causes it to be "hoisted" (See "Function Declaration Hoisting").

After that, you'll notice that you get a subsequent error:

Expected listener to be a function.

on store.subscribe(App);. This is because class declarations aren't hoisted (see "Hoisting"). So you'll want the class declaration of App before store.subscribe(App);.

Upvotes: 3

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