sag1v

let _previousKey;

function Pets() {
  //... 

  useEffect(() => {
    _previousKey = pets.selectedPet;
    if (pets.selectedPet) {
      dispatch({ type: "FETCH_PET" });
      getPet(pets.selectedPet).then(data => {

sag1v

function Pets() {
  //...
  const _previousKeyRef = useRef(null);

  useEffect(() => {
    _previousKeyRef.current = pets.selectedPet;
    if (pets.selectedPet) {
      dispatch({ type: "FETCH_PET" });
      getPet(pets.selectedPet).then(data => {
        if (_previousKeyRef.current === pets.selectedPet) {

sag1v

useEffect(() => {
  let abort = false;

  if (pets.selectedPet) {
    dispatch({ type: "FETCH_PET" });
    getPet(pets.selectedPet).then(data => {
      if(!abort){
        dispatch({ type: "FETCH_PET_SUCCESS", payload: data });
      }
    });

sag1v

const initialState = { loading: false, selectedPet: "", petData: null }

function petsReducer(state, action) {
  switch (action.type) {
    case "PET_SELECTED": {
      return {
        ...state,
        selectedPet: action.payload
      };
    }

sag1v

useEffect(() => {
  let _previousKey = pets.selectedPet;
  if (pets.selectedPet) {
    dispatch({ type: "FETCH_PET" });
    getPet(pets.selectedPet).then(data => {
      if (_previousKey === pets.selectedPet) {
        dispatch({ type: "FETCH_PET_SUCCESS", payload: data });
      }
    });
  } else {

sag1v

const petsDB = {
  dogs: { name: "Dogs", voice: "Woof!", avatar: "🐶" },
  cats: { name: "Cats", voice: "Miauuu", avatar: "🐱" }
};

export function getPet(type) {
  return new Promise(resolve => {
    // simulate a fetch call
    setTimeout(() => {
      resolve(petsDB[type]);

sag1v

function Pets() {
  const [pets, dispatch] = useReducer(petsReducer, initialState);

  const onChange = ({ target }) => {
    dispatch({ type: "PET_SELECTED", payload: target.value });
  };

  useEffect(() => {
    if (pets.selectedPet) {
      dispatch({ type: "FETCH_PET" });

sag1v

export function getPet(type) {
  const delay = type === "cats" ? 3500 : 500;
  return new Promise(resolve => {
    // immulate fetch call
    setTimeout(() => {
      resolve(petsDB[type]);
    }, delay);
  });
}

sag1v

  useEffect(() => {
    if (pets.selectedPet) {
      dispatch({ type: "FETCH_PET" });
      getPet(pets.selectedPet).then(data => {
        dispatch({ type: "FETCH_PET_SUCCESS", payload: data });
      });
    } else {
      dispatch({ type: "RESET" });
    }
  }, [pets.selectedPet]);

sag1v

class Player {

}