End-to-end typing for REST APIs with TypeScript
Motivation
Typescript is a one-way street: Once you start using it, it's hard to go back to plain JS. In fact, you'll probably want to write your entire application in TypeScript.
After happily typing all of your models, you notice that there's a disconnect: Your types don't make it over the wire! The server doesn't check types before it sends an HTTP response, and the client doesn't know what types it's receiving. Conversely, the server doesn't know what types it should receive, and the client doesn't know what to send.
RESTyped was designed to brige the gap by creating an easy way to share types across your API server and any public or private clients.
Benefits
- End to end typing. Share request and response types between your client and server for ease of use and peace of mind
- Unopinionated. Works with any new or existing REST API
- Universal. Can support any server framework or REST client
- Lightweight. Most server and client implementations don't even add any code--just types
- Use existing syntax. Write your REST routes and clients the same way you always have
- Great for private APIs. Keep API clients across your organization in sync with the latest changes
- Great for public APIs. Create an API definition so TypeScript users can consume your API fully typed
- Easy to learn and use. Start using RESTyped in typically less than one minute per route
How to use it
RESTyped is a specification. Once you spend a few minutes typing your API using the spec below, you can use these server and client typings to declare and consume your API in a type-safe manner:
You can help make RESTyped more useful by typing your favorite server framework or HTTP client!
RESTyped requires TypeScript 2.4 or higher.
Specification
It's very easy to get started with RESTyped. Just follow a few steps to type your existing API or create a new typed API:
- Your API should be defined in one interface, exported as
{my_api_name}API
from a file ending in .d.ts
- Each route is a top level key in the interface. You should exclude any prefixes like
/api/
. - Each route can have up to one key per valid HTTP method:
GET
, POST
, PUT
, PATCH
, DELETE
, HEAD
or OPTIONS
- Each HTTP method can have one or more of the following keys:
params
: Route params in the URL (e.g. /users/:id
would have id
as a param)query
: Query string params, typically used in GET
requests (e.g. req.query
in express)body
: JSON body object (e.g. req.body
in express or data
object in an axios request)response
: The route's JSON response
Example: my-social-api.d.ts
interface User {
email: string
name: string
gender: 'Male' | 'Female' | 'Other'
}
export interface MySocialAPI {
'/users': {
GET: {
query: {
includeProfilePics?: boolean
}
response: User[]
}
}
'/user/:id/send-message': {
POST: {
params: {
id: string
}
body: {
message: string
}
response: {
success: boolean
}
}
}
}
Full-Stack Example
export interface FoodDeliveryAPI {
'/me/orders': {
POST: {
body: {
foodItemIds: string[]
address: string
paymentMethod: 'card' | 'cash'
paymentCardId?: string
}
response: {
success: boolean
eta?: string
}
}
}
}
2. Declare the API via express
import {AsyncRouter} from 'restyped-express'
import {FoodDeliveryAPI} from './food-delivery-api'
import OrderModel from './controllers/order'
const route = AsyncRouter<FoodDeliveryAPI>('/api/')
route.post('/me/orders', async (req) => {
const {foodItemId, address} = req.body
const success = await OrderModel.order(foodItemId, address)
return {success}
})
3. Consume the API via axios
import axios from 'restyped-axios'
import {FoodDeliveryAPI} from './food-delivery-api'
const api = axios.create({baseURL: 'https://fooddelivery.com/api/'})
async function order() {
const res = await api.post(
'/me/orders',
{
foodItemIds: ['QbY7Nmx1', '34YthU3m'],
address: '1601 Market St, Phiadelphia, PA 19103',
paymentMethod: 'cash'
}
)
const {success, eta} = res.data
}
What RESTyped isn't
- A replacement for API docs. A RESTyped spec will help you get the routes and types right, but doesn't provide the context or say anything about the content of API requests and responses.
Popular APIs to try out