Skip to main content


Endpoint are for any asynchronous function (one that returns a Promise).

Endpoints define a strongly typed standard interface of relevant metadata and lifecycles useful for Reactive Data Client and other stores.

Package: @data-client/endpoint


Endpoint is a protocol independent class. Try using the protocol specific patterns REST, GraphQL, or getImage instead.

export interface EndpointInterface<
F extends FetchFunction = FetchFunction,
S extends Schema | undefined = Schema | undefined,
M extends true | undefined = true | undefined,
> extends EndpointExtraOptions<F> {
(...args: Parameters<F>): InferReturn<F, S>;
key(...args: Parameters<F>): string;
readonly sideEffect?: M;
readonly schema?: S;


Endpoint makes existing async functions usable in any Reactive Data Client context with full TypeScript enforcement.

import { Todo } from './interface';

const getTodoOriginal = (id: number): Promise<Todo> =>
    title: 'delectus aut autem ' + id,
    completed: false,
    userId: 1,

export const getTodo = new Endpoint(getTodoOriginal);
import { getTodo } from './api';

function TodoDetail() {
  const todo = useSuspense(getTodo, 1);
  return <div>{todo.title}</div>;
render(<TodoDetail />);
🔴 Live Preview

Configuration sharing

Use Endpoint.extend() instead of {...getTodo} (spread)

const getTodoNormalized = getTodo.extend({ schema: Todo });
const getTodoUpdatingEveryFiveSeconds = getTodo.extend({ pollFrequency: 5000 });




Endpoint Members

Members double as options (second constructor arg). While none are required, the first few have defaults.

key: (params) => string

Serializes the parameters. This is used to build a lookup key in global stores.


`${} ${JSON.stringify(params)}`;

When overriding key, be sure to also include an updated testKey if you intend on using that method.

testKey(key): boolean

Returns true if the provided (fetch) key matches this endpoint.

This is used for mock interceptors with with <MockResolver />

name: string

Used in key to distinguish endpoints. Should be globally unique.

Defaults to


This may break in production builds that change function names. This is often know as function name mangling.

In these cases you can override name or disable function mangling.

sideEffect: boolean

Used to indicate endpoint might have side-effects (non-idempotent). This restricts it from being used with useSuspense() or useFetch() as those can hit the endpoint an unpredictable number of times.

schema: Schema

Declarative definition of how to process responses

Not providing this option means no entities will be extracted.

import { Entity } from '@data-client/normalizr';
import { Endpoint } from '@data-client/endpoint';

class User extends Entity {
readonly id: string = '';
readonly username: string = '';

pk() { return;}

const getUser = new Endpoint(
({ id })fetch(`/users/${id}`),
{ schema: User }


dataExpiryLength?: number

Custom data cache lifetime for the fetched resource. Will override the value set in NetworkManager.

Learn more about expiry time

errorExpiryLength?: number

Custom data error lifetime for the fetched resource. Will override the value set in NetworkManager.

errorPolicy?: (error: any) => 'soft' | undefined

'soft' will use stale data (if exists) in case of error; undefined or not providing option will result in error.

Learn more about errorPolicy

errorPolicy(error) {
return error.status >= 500 ? 'soft' : undefined;

invalidIfStale: boolean

Indicates stale data should be considered unusable and thus not be returned from the cache. This means that useSuspense() will suspend when data is stale even if it already exists in cache.

pollFrequency: number

Frequency in millisecond to poll at. Requires using useSubscription() or useLive() to have an effect.

getOptimisticResponse: (snap, ...args) => fakePayload

When provided, any fetches with this endpoint will behave as though the fakePayload return value from this function was a succesful network response. When the actual fetch completes (regardless of failure or success), the optimistic update will be replaced with the actual network response.

import { resource } from '@data-client/rest';
import { Post } from './Post';

export { Post };

export const PostResource = resource({
  path: '/posts/:id',
  searchParams: {} as { userId?: string | number } | undefined,
  schema: Post,
}).extend('vote', {
  path: '/posts/:id/vote',
  method: 'POST',
  body: undefined,
  schema: Post,
  getOptimisticResponse(snapshot, { id }) {
    const post = snapshot.get(Post, { id });
    if (!post) throw snapshot.abort;
    return {
      votes: post.votes + 1,
🔴 Live Preview
Optimistic update guide


(normalizedResponseOfThis, ...args) =>
({ [endpointKey]: (normalizedResponseOfEndpointToUpdate) => updatedNormalizedResponse) })

Try using Collections instead.

They are much easier to use and more robust!

type UpdateFunction<
Source extends EndpointInterface,
Updaters extends Record<string, any> = Record<string, any>,
> = (
source: ResultEntry<Source>,
...args: Parameters<Source>
) => { [K in keyof Updaters]: (result: Updaters[K]) => Updaters[K] };

Simplest case:

const createUser = new RestEndpoint({
path: '/user',
method: 'POST',
schema: User,
update: (newUserId: string) => ({
[userList.key()]: (users = []) => [newUserId, ...users],

More updates:

const allusers = useSuspense(userList);
const adminUsers = useSuspense(userList, { admin: true });

The endpoint below ensures the new user shows up immediately in the usages above.

const createUser = new RestEndpoint({
path: '/user',
method: 'POST',
schema: User,
update: (newUserId, newUser) => {
const updates = {
[userList.key()]: (users = []) => [newUserId, ...users],
if (newUser.isAdmin) {
updates[userList.key({ admin: true })] = (users = []) => [newUserId, ...users];
return updates;

extend(EndpointOptions): Endpoint

Can be used to further customize the endpoint definition

const getUser = new Endpoint(({ id })fetch(`/users/${id}`));

const getUserNormalized = getUser.extend({ schema: User });

In addition to the members, fetch can be sent to override the fetch function.


import { Endpoint } from '@data-client/endpoint';

const UserDetail = new Endpoint(
({ id })fetch(`/users/${id}`).then(res => res.json())
function UserProfile() {
const user = useSuspense(UserDetail, { id });
const ctrl = useController();

return <UserForm user={user} onSubmit={() => ctrl.fetch(UserDetail)} />;



There is a distinction between

  • What are networking API is
    • How to make a request, expected response fields, etc.
  • How it is used
    • Binding data, polling, triggering imperative fetch, etc.

Thus, there are many benefits to creating a distinct seperation of concerns between these two concepts.

With TypeScript Standard Endpoints, we define a standard for declaring in TypeScript the definition of a networking API.

  • Allows API authors to publish npm packages containing their API interfaces
  • Definitions can be consumed by any supporting library, allowing easy consumption across libraries like Vue, React, Angular
  • Writing codegen pipelines becomes much easier as the output is minimal
  • Product developers can use the definitions in a multitude of contexts where behaviors vary
  • Product developers can easily share code across platforms with distinct behaviors needs like React Native and React Web

What's in an Endpoint

  • A function that resolves the results
  • A function to uniquely store those results
  • Optional: information about how to store the data in a normalized cache
  • Optional: whether the request could have side effects - to prevent repeat calls