Nano Stores Query

A tiny data fetcher for Nano Stores.

• Small. 1.59 Kb (minified and gzipped).
• Familiar DX. If you've used swr or react-query, you'll get the same treatment, but for 10-20% of the size.
• Built-in cache. stale-while-revalidate caching from HTTP RFC 5861. User rarely sees unnecessary loaders or stale data.
• Revalidate cache. Automaticallty revalidate on interval, refocus, network recovery. Or just revalidate it manually.
• Nano Stores first. Finally, fetching logic outside of components. Plays nicely with store events, computed stores, router, and the rest.
• Transport agnostic. Use GraphQL, REST codegen, plain fetch or anything, that returns Promises.

Install

npm install nanostores @nanostores/query

Usage

See Nano Stores docs about using the store and subscribing to store’s changes in UI frameworks.

Context

First, we define the context. It allows us to share the default fetcher implementation between all fetcher stores, refetching settings, and allows for simple mocking in tests and stories.

// store/fetcher.ts
import { nanoquery } from '@nanostores/query';

export const [createFetcherStore, createMutatorStore] = nanoquery({
  fetcher: (...keys: string[]) => fetch(keys.join('')).then((r) => r.json()),
});

Second, we create the fetcher store. createFetcherStore returns the usual atom() from Nano Stores, that is reactively connected to all stores passed as keys. Whenever the $currentPostId updates, $currentPost will call the fetcher once again.

// store/posts.ts
import { createFetcherStore } from './fetcher';

export const $currentPostId = atom('');
export const $currentPost = createFetcherStore<Post>(['/api/post/', $currentPostId]);

Third, just use it in your components. createFetcherStore returns the usual atom() from Nano Stores.

// components/Post.tsx
const Post = () => {
  const { data, loading } = useStore($currentPost);
  if (loading) return <>Loading...</>;
  if (!data) return <>Error!</>;

  return <div>{data.content}</div>;
};

createFetcherStore

export const $currentPost = createFetcherStore<Post>(['/api/post/', $currentPostId]);

It accepts two arguments: key and fetcher options.

type KeyParts = undefined | Array<ReadableAtom<string | null | undefined> | string>

Under the hood, nanoquery will get the string values and pass them to your fetcher like this: fetcher(...keyPartsAsStrings). If any atom value is either null or undefined, we never call the fetcher—this is the conditional fetching technique we have.

type Options = {
  // The async function that actually returns the data
  fetcher?: (...keyParts: string[]) => Promise<unknown>;
  // How much time should pass between running fetcher for the exact same key parts
  // default = 4s
  dedupeTime?: number;
  // If we should revalidate the data when the window focuses
  // default = false
  refetchOnFocus?: boolean;
  // If we should revalidate the data when network connection restores
  // default = false
  refetchOnReconnect?: boolean;
  // If we should run revalidation on an interval, in ms
  // default = 0, no interval
  refetchInterval?: number;
}

The same options can be set on the context level where you actually get the createFetcherStore.

createMutatorStore

Mutator basically allows for 2 main things: tell nanoquery what data should be revalidated and optimistically change data. From interface point of view it's essentially a wrapper around your async function with some added functions.

It gets an object with 3 arguments:

• data is the data you pass to the mutate function;
• invalidate allows you to mark other keys as stale so they are refetched next time;
• getCacheUpdater allows you to get current cache value by key and update it with a new value. The key is also invalidated by default.

export const $addComment = createMutatorStore<Comment>(
  async ({ data: comment, invalidate, getCacheUpdater }) => {
    // You can either invalidate the author…
    invalidate(`/api/users/${comment.authorId}`);

    // …or you can optimistically update current cache.
    const [updateCache, post] = getCacheUpdater(`/api/post/${comment.postId}`);
    updateCache({ ...post, comments: [...post.comments, comment] });

    // Even though `fetch` is called after calling `invalidate`, we will only
    // invalidate the keys after `fetch` resolves
    return fetch('…')
  }
);

The usage in component is very simple as well:

const AddCommentForm = () => {
  const { mutate, loading, error } = useStore($addComment);

  return (
    <form
      onSubmit={(e) => {
        e.preventDefault();
        mutate({ postId: "…", text: "…" });
      }}
    >
      <button disabled={loading}>Send comment</button>
      {error && <p>Some error happened!</p>}
    </form>
  );
};

Third returned item

(we didn't come up with a name for it 😅)

nanoquery function returns a third item that gives you a bit more manual control over the behavior of the cache.

// store/fetcher.ts
import { nanoquery } from '@nanostores/query';

export const [,, { invalidateKeys, mutateCache }] = nanoquery();

invalidateKeys does 2 things:

1. nukes all cache for the specified keys;
2. asks all the fetcher stores that used those keys to refresh data immediately, if they have active subscribers.

It accepts one argument—the keys—in 3 different forms, that we call key selector.

// Single key
invalidateKeys("/api/whoAmI");
// Array of keys
invalidateKeys(["/api/dashboard", "/api/projects"]);
/**
 * A function that will be called against all keys in cache.
 * Must return `true` if key should be invalidated.
 */
invalidateKeys((key) => key.startsWith("/api/job"));

mutateCache does one thing only: it mutates cache for those keys and refreshes all fetcher stores that have those keys currently.

/**
 * Accepts key in the same form as `invalidateKeys`: single, array and a function.
 */
mutateCache((key) => key === "/api/whoAmI", { title: "I'm Batman!" });

Keep in mind: we're talking about the serialized singular form of keys here. You cannot pass stuff like ['/api', '/v1', $someStore], it needs to be the full key in its string form.

Recipes

Local state and Pagination

All examples above use module-scoped stores, therefore they can only have a single data point stored. But what if you need, say, a store that fetches data based on component state? Nano Stores do not limit you in any way, you can easily achieve this by creating a store instance limited to a single component:

const createStore = (id: string) => () =>
  createFetcherStore<{ avatarUrl: string }>(`/api/user/${id}`);

const UserAvatar: FC<{ id: string }> = ({ id }) => {
  const [$user] = useState(createStore(id));

  const { data } = useStore($user);
  if (!data) return null;

  return <img src={data.avatarUrl} />;
};

This way you can leverage all nanoquery features, like cache or refetching, but not give up the flexibility of component-level data fetching.

Refetching and manual mutation

We've already walked through all the primitives needed for refetching and mutation, but the interface is rather bizarre with all those string-based keys. Often all we actually want is to refetch current key (say, you have this refresh button in the UI), ot mutate current key, right?

For these cases we have 3 additional things on fetcher stores:

1. fetcherStore.invalidate. It's a function that invalidates current key for the fetcher. Doesn't accept any arguments.
2. fetcherStore.mutate. It's a function that mutates current key for the fetcher. Accepts the new value.
3. fetcherStore.key. Well, it holds current key in serialized form (as a string).

Typically, those 3 are more than enough to make all look very good.

Dependencies, but not in keys

Let's say, you have a dependency for your fetcher, but you don't wish for it to be in your fetcher keys. For example, this could be your refreshToken—that would be a hassle to put it everywhere, but you need it, because once you change your user, you don't want to have stale cache from the previous user.

The idea here is to wipe the cache manually. For something as big as a new refresh token you can go and do a simple "wipe everything you find":

onSet($refreshToken, () => invalidateKeys(() => true))

But if your store is somehow dependant on other store, but it shouldn't be reflected in the key, you should do the same, but more targetly:

onSet($someOutsideFactor, $specificStore.invalidate)