When working with data in React applications, you often need a reliable way to fetch, cache, and manage server state. The useQuery hook from TanStack Query is designed to handle these tasks efficiently. You use useQuery to fetch data from APIs, automatically manage caching, and keep your UI in sync with the server.

The basic syntax for useQuery looks like this:

const { data, error, isLoading, isSuccess, isError } = useQuery({
  queryKey,
  queryFn,
  ...options
})

• The query key (queryKey) is a unique identifier for the data you are fetching. It can be a string or an array of strings and variables;
• The fetch function (queryFn) describes how to fetch the data, usually returning a promise;
• The options object lets you customize query behavior, such as refetching intervals or caching strategies.

The hook returns an object containing several properties:

• data: the data returned from your fetch function (or undefined if not loaded yet);
• error: an error object if the fetch failed;
• isLoading: true if the query is currently loading;
• isSuccess: true if the query completed successfully;
• isError: true if the query failed.