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If you're developing a client & server app both in TypeScript, you can leverage TypePoint to DRYly define your RESTful API endpoints to have strongly typed requests and responses, without duplicating or generating code.

• Strongly typed requests and responses, both on client and server!
• Endpoints are defined only once
• No code generation!
• Validation of request params and body
• Promise based request handlers & middleware
• Support for React Hooks

First we need to install the following packages:

npm add @typepoint/client @typepoint/server @typepoint/shared @typepoint/express

We start by defining an endpoint in a shared folder. Our example will define an endpoint to return a Todo with a given id passed as a path param.

import { defineEndpoint, Empty } from '@typepoint/shared';

export interface Todo {
  id: string;
  title: string;
  isCompleted: boolean;
}

export interface GetTodoRequestParams {
  id: string;
}

export const getTodoEndpoint = defineEndpoint<GetTodoRequestParams, Empty, Todo[]>((path) =>
  path.literal('/api/todos/').param('id'),
);

Our getTodoEndpoint variable defines our endpoint, including:

• The HTTP method (defaults to 'GET')
• The path to the endpoint: '/api/todos/{id}'
• The request params type: GetTodoRequestParams
• The request body type: Empty (no body, because its a GET method)
• The response body: Todo

Next, let's create a handler for our endpoint in our server.

import { createHandler } from '@typepoint/server';
import { getTodoEndpoint } from '../../shared/endpoints/getTodoHandler';
import { getTodoById } from './todoService';

export const getTodoHandler = createHandler(getTodoEndpoint, async ({ request, response }) => {
  // Get todo from our async todo service and put it in our response body
  response.body = await getTodoById(request.params.id);
});

Next we need to create a router in order to route requests to our handlers.

import { Router } from '@typepoint/server';
import { getTodoHandler } from './todos/getTodoHandler';

export const router = new Router({
  // We just have one handler for now
  handlers: [getTodoHandler],
});

Finally, we need to connect our router to our web server.

import express = require('express');
import * as bodyParser from 'body-parser';

import { toMiddleware } from '@typepoint/express';
import { router } from './router';

async function run() {
  const app = express();
  const port = 3001;

  app.use(bodyParser.json());

  const handlerMiddleware = toMiddleware(router);
  app.use(handlerMiddleware);

  app.listen(port, () => {
    console.log(`API Server running at http://localhost:${port}`);
  });
}

run().catch(console.error);

Now if we run ts-node ./server we'll have a working server that will handle getting a todo.

On the front-end, we need to create a Client in order to make requests.

import { TypePointClient } from '@typepoint/client';

export const client = new Client({
  server: 'http://localhost:3001',
});

Now we have our TypePointClient created, we can use it anywhere in our front-end.

import { client } from './typepoint';
import { getTodoEndpoint } from '../shared/endpoints/getTodoEndpoint';

async function showTodo() {
  const response = await client.fetch(getTodoEndpoint, {
    params: {
      id: '1',
    },
  });

  const todo = response.body;

  alert(todo.title);
}

The above client side code is completely typed. Trying to fetch from the getTodoEndpoint without passing the a string id as a param will cause a design/compile-time error. The response is also completely typed.

The @typepoint/react library provides react hooks to call your endpoints.

npm add @typepoint/react

Before you can start using TypePoint React hooks, you'll need to wrap your root component with a TypePointProvider. This provides the client that the hooks will use.

import * as React from 'react';
import * as ReactDOM from 'react-dom';
import { TypePointClient } from '@typepoint/client';
import { TypePointProvider } from '@typepoint/react';
import { App } from './app';

const client = new TypePointClient({
  // Path to API server, normally this will be an environment variable
  server: 'http://localhost:3001',
});

export const AppWithProviders = React.memo(() => (
  <TypePointProvider client={client}>
    <App />
  </TypePointProvider>
));

const root = window.document.getElementById('root');

ReactDOM.render(<AppWithProviders />, root);

useEndpoint is a hook that immediately fetches a given endpoint with the given params and or body.

import React from 'react';
import { useEndpoint } from '@typepoint/react';
import { getTodosEndpoint } from '../shared/endpoints/getTodosEndpoint';

const TodoApp = () => {
  const { response } = useEndpoint(getTodosEndpoint, {});
  const todos = response?.body ?? [];

  return (
    <ul>
      {todos.map((todo) => (
        <li key={todo.id}>{todo.title}</li>
      ))}
    </ul>
  );
};

export default TodoApp;

The endpoint will not be fetched unnecessarily, only when the params change. In the above example no params are required so it will only be fetched once.

useEndpoint also returns a refetch function which can be called imperatively to refetch the endpoint with the last used params and body. This is useful for refreshing data.

const { response, refetch } = useEndpoint(getTodosEndpoint, {});

useEndpoint also returns the loading state of the request, as well as an error if there is one.

const TodoApp = () => {
  const { response } = useEndpoint(getTodosEndpoint, {});
  const { response, loading, error } = useEndpoint(getTodosEndpoint, {});

  if (loading) {
    return <Spinner />;
  }

  if (error) {
    return <div>Something went wrong!</div>;
  }

  const todos = response?.body ?? [];

  return (
    <ul>
      {todos.map((todo) => (
        <li key={todo.id}>{todo.title}</li>
      ))}
    </ul>
  );
};

useEndpointLazily is just like useEndpoint except that it does not immediately fetch the endpoint, instead it provides a fetch function to let you fetch the given endpoint on demand.

import React from 'react';
import { useEndpointLazily } from '@typepoint/react';
import { addTodoEndpoint } from '../shared/endpoints/addTodoEndpoint';

/**
 * Component which can create a new todo.
 */
const NewTodoInput = () => {
  const [title, setTitle] = useState('');

  const { fetch: addTodo } = useEndpointLazily(addTodoEndpoint);

  const addTodoWithTitle = useCallback((title: string) => {
    addTodo({ body: { title } });
  }, [addTodo]);

  return (
    <div>
      <input type="text" value=>
      <button type="button" onClick={addTodoWithTitle}>Add</button>
    </div>
  );
};

export default TodoApp;

Check out the examples repository for example apps that use TypePoint.

• Todo app using Express & React
• Todo app using Next.js & React

Got a problem or suggestion? Submit an issue!

Want to contribute? Fork the repository and submit a pull request! 🌩