bridge

What is Bridge?

Bridge is a Typescript Node.js framework that provides an easy and scalable way to create REST APIs while generating the client code.

Our goal is to make Bridge a great framework for both frontend and backend teams, so if you're familiar with Node.js and Typescript, you'll feel right at home.

👉 See more informations on bridge.codes 👈

Table of Contents

1. What is Bridge
2. Quickstart
3. Init Bridge 4. Routing 5. Handler 6. Middleware 7. Error handling

Quickstart

There are a few examples that you can use for playing out with Bridge or start your new project.

Using create-bridge-app

The easiest way to start a Bridge project is by using create-bridge-app. It will initialize a project and install all required dependencies. Open your terminal, go into the directory you’d like to create the app in, and run the following command:

npx create-bridge-app

When the installation is done, you can run the project using the default settings with the following command:

npm run build && npm run start

This builds and starts your Bridge "server" on port 8080.

Manual setup with Express

Init your project and install all required dependencies.

npm init
npm i bridge express
npm i typescript @types/express --save-dev

Create an index.ts file.

import { handler, initBridge } from 'bridge';
import express from 'express';

const port = 8080;

const helloHandler = handler({ method: 'GET', resolve: () => 'hello' });

const routes = {
  hello: helloHandler,
};

const app = express();

app.use('', initBridge({ routes: routes }).expressMiddleware());

app.listen(port, () => {
  console.log(`Listening on port ${port}`);
});

Init Bridge

First you will need to initialize bridge app. You can either use it with express or with HTTPServer. This will make your Bridge endpoints available.

If you use express

import { handler, initBridge } from 'bridge';
import express from 'express';

const port = 8080;
const routes = {
  hello: handler({
    method: 'GET',
    resolve: () => 'hello',
  }),
};

const app = express();

app.use('', initBridge({ routes: routes }).expressMiddleware());

app.listen(port, () => {
  console.log(`Listening on port ${port}`);
});

With HTTPServer

import { handler, initBridge } from 'bridge';

const port = 8080;
const routes = { hello: handler({ method: 'GET', resolve: () => 'hello' }) };

initBridge({ routes })
  .HTTPServer()
  .listen(port, () => {
    console.log(`Listening on port ${port}`);
  });

Routing

Handlers themselves cannot be be directly called. They have to be addded to an object that we call router and this object has to be passed to the initBridge function.

The keys in your router object are the different endpoints of your API while the values associated with those keys and the values are the handlers that will be executed when a request is made to the corresponding endpoint.

Example

import { handler } from 'bridge';

const helloHandler = handler({
  method: 'GET',
  resolve: () => {
    return 'Hello';
  },
});

const byeHandler = handler({
  // default method is POST
  resolve: () => {
    return 'Bye';
  },
});

const routes = {
  // GET /hello
  hello: myFirstHandler,
  // POST /bye
  bye: byeHandler,
};

Don't forget to pass the router as a param to the initBridge function as seen in initBridge.

Nested routes

In addition to defining individual routes, you can also create nested routes by adding new objects to your router.

Nested routes allow you to create more complex and organized APIs by grouping related routes together.

const routes = {
  admin: {
    users: {
      // POST /admin/users/create
      create: createUserHandler,
      // POST /admin/users/get
      get: getUserHandler,
      // POST /admin/users/update
      update: updateUserHandler,
    },
  },
};

Handler

Bridge provides the handler. It it a function responsible for several things:

• Validate data coming from the client
• If an errors occurs or the request is invalid, notify the client
• Return a response to the client

Basic example

import { handler } from 'bridge';

const myFirstHandler = handler({
  method: 'GET',
  resolve: () => {
    const response = { response: 'Hello World' };
    return response;
  },
});

Data validation

The validation is done using the zod library. Other libraries like superstruct or yup are also supported. Make sure you have zod installed:

npm install zod

You can validate the body, headers and query of each requet using zod. If the request doesn't meet the validation criteria, a 422 error is automatically sent to the client. The response sent will explain where the validation failed.

The validation takes this form

const userHandler = handler({
  // ...
  body: z.object({
    name: z.string(),
    age: z.number(),
    // the body can contain objects, dates, strings, numbers, arrays, ...
  }),
  query: z.object({
    // the query can only contain string validation as value
    param1: z.string(),
    param2: z.string(),
    // ...
  }),
  headers: z.object({
    haeder1: z.string(),
    header2: z.string(),
    // the headers can only contain string validation
  }),
  resolve: ({ body, query, headers }) => {
    //...
  },
});

Here is an example:

// You can use either zod, yup or superstruct
import z from 'zod';
import { handleri } from 'bridge';

const hello = handler({
  query: z.object({ name: z.string().optional() }),
  body: z.object({ age: z.number() }),
  headers: z.object({ token: z.string().min(6) }),
  resolve: ({ query, body, headers }) => `Hello ${query.name}`,
});

Type inference

The types of the validated query, body and headers as long as the return of the middlewares are automatically infered. You can use these objects inside the resolve function of the handler.

Middleware

A middleware is handler function that is called before the resolve function of the main handler of the called endpoint. Creating a middleware is just as simple as creating a handler. In fact, it is a handler function which means that the middleware can perform the exact same tasks.

The return of the middleware is returned into the mid object of the resolve function of the main handler. Its type is infered.

Example

import z from 'zod';
import { apply, handler } from 'bridge';

const authMiddleware = handler({
  headers: z.object({ token: z.string().min(5) }),
  resolve: ({ headers }) => {
    if (headers.token !== 'private_token') return httpError(StatusCode.UNAUTHORIZED, 'Wrong token');
    else return { firstName: 'John', name: 'Doe', age: 21 };
  },
});

const updateUser = handler({
  middlewares: apply(authMiddleware),
  body: z.object({ age: z.number() }),
  resolve: ({ mid, body }) => {
    const user = mid;
    user.age = body.age;
    return user;
  },
});

Error handling

Bridge has 2 ways of sending errors:

• Data validation errors
• Manual triggered errors

The first method is managed by zod, superstruct or yup while the second one has to be written manually.

Send an HTTP error

import { httpError, StatusCode } from "bridge";

const getMe: handler({
  headers: z.object({ token: z.string().min(6) }),
  resolve: ({ headers }) => {
    if (headers.token !== "private_token") return httpError(StatusCode.UNAUTHORIZED, 'Wrong token');
    else return {
      firstName: 'John',
      lastName: 'Doe',
    }
  },
}),

Monitor errors

import { initBridge, onError } from 'bridge';
const errorHandler = onError(({ error, path }) => {
  if (error.name === 'Internal server error') console.log(path, error); // Send to bug reporting
  else console.log(path, error.status, error.name);
});

const bridge = initBridge({ routes, errorHandler });