In this app we demonstrate few fundamental concepts of handling API concepts in React.

Selects a pokemon option from a dropdow and makes a single API call for each selection. This is done using only Axios as an external library and vanilla React.

• ChangeEvent is a built-in type for event handlers
• pokemonData stores the fetched data
• setSelectedPokemon tracks the currently selected pokemon's name (string)
• setPokemonData a function to update pokemonData

ChangeEvent: Type from React, used for typing the event in event handlers.

• useState is used to manage the dropdown state and the fetched data

• useEffect to make the API call when the dropdown values changes, but only if the data hasn't been fetched before

• selectedPokemon state is updated when we select something from the dropdown.

const [selectedPokemon, setSelectedPokemon] = useState("");

• useEffect hook listens for changes to selectedPokemon
• it is triggered when pokemonData or selectedPokemon changes.
• when you select a pokemon (selectedPokemon) and no data is loaded (!pokemonData) an API call is made fetching the data about that selected pokemon.
• the double dependency is an extra safe way to control the effect:
• it runs whenever the state of selectedPokemon changes
• this happens on selection from the dropdown
• the API call is made
• pokemonData seems redundant but it is not. We check if pokemonData is null before making the API call. This ensure the API call is made only if the data isn't already fetched. Hence, no wasted API calls.
• pokemonData is a safeguard - this practice is optional, but recommended.

useEffect(() => {
  if (selectedPokemon && !pokemonData) {
    axios
      .get(`https://pokeapi.co/api/v2/pokemon/${selectedPokemon}`)
      .then((response) => {
        setPokemonData(response.data);
      })
      .catch((error) => console.error("Error fetching data:", error));
  }
}, [pokemonData, selectedPokemon]);

• when selectedPokemon is udpated, and pokemonData is null it means no data has been fetched,and therfore an API call is made for to fetch the data of the selected pokemon.
• the data is stored in pokemonData and this persists across renders.

• when a different pokemon is selectd, pokemonData is reset to null by handleSelect to allow a new fetch.

const handleSelect = (event) => {
  setPokemonData(null);
  setSelectedPokemon(event.target.value);
};

• useState<string>(""): Initializes selectedPokemon as an empty string.
• useState<PokemonData | null>(null): Initializes pokemonData as null. PokemonData is likely a custom interface or type representing the structure of the data received from the Pokémon API.

• useEffect is used for side effects, in this case, fetching data when the selected Pokémon changes.
• The API call is made only if a Pokémon is selected (selectedPokemon) and pokemonData is not already fetched.
• axios.get makes a GET request to the Pokémon API.
• The dependency array [pokemonData, selectedPokemon] means this effect runs when either pokemonData or selectedPokemon changes.

• handleSelect is an event handler for the <select> element.
• When a new Pokémon is selected, it resets pokemonData to null and sets selectedPokemon to the selected value.

• The component conditionally renders Pokémon data (<h3> for the name and an <img> for the sprite) if pokemonData is available.

• The dropdown contains hardcoded options for Pokémon like "Pikachu", "Charmander", and "Bulbasaur".
• More options can be added similarly.

This component is a typical example of a React functional component utilizing hooks for state management and side effects. It demonstrates fetching and displaying data based on user input, a common pattern in React applications.