Koa-zod-router NPM

⚡ koa-zod-router ⚡

Inspired by koa-joi-router, this package aims to provide a similar feature-set while leveraging Zod and Typescript to create a fantastic dev experience.

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🔥 Features:

Input/output validation and typesafety using zod
Body parsing using koa-bodyparser
Multipart parsing using formidable
Wraps @koa/router, providing the same API but with typesafety and validation.
CJS and ESM support

🚀 Install

npm install koa-zod-router

🚦 Quickstart

index.ts:

import Koa from 'koa';
import zodRouter from 'koa-zod-router';
import { z } from 'zod';

const app = new Koa();

const router = zodRouter();

router.register({
  name: 'example',
  method: 'post',
  path: '/post/:id',
  handler: async (ctx, next) => {
    const { foo } = ctx.request.body;
    ctx.body = { hello: 'world' };

    await next();
  },
  validate: {
    params: z.object({ id: z.coerce.number() }),
    body: z.object({ foo: z.number() }),
    response: z.object({ hello: z.string() }),
  },
});

app.use(router.routes());

app.listen(3000, () => {
  console.log('app listening on http://localhost:3000');
});

Importing/Exporting routes

Most likely you'll want to seperate your routes into seperate files, and register them somewhere in your app's initialization phase. To do this you can use the helper function createRouteSpec and specify the route's properties.

get-user.ts:

import { createRouteSpec } from 'koa-zod-router';
import { z } from 'zod';

export const getUserRoute = createRouteSpec({
  method: 'get',
  path: '/user/:id',
  handler: (ctx) => {
    ctx.body = {
      /* payload here */
    };
  },
  validate: {
    params: z.object({ id: z.coerce.number() }),
    response: z.object({
      /* validation here */
    }),
  },
});

index.ts:

import zodRouter from 'koa-zod-router';
import { getUserRoute } from './get-user.ts';

const router = zodRouter();
router.register(getUserRoute);

Exposing validation errors to the client

By default validation errors will respond with either a generic 400 or 500 error depending on whether the validation fails from the sent fields in the request, or if there is an issue in the response body.

To enable ZodErrors being exposed to the client simply use the following config:

const router = zodRouter({
  zodRouter: { exposeRequestErrors: true, exposeResponseErrors: true },
});

Type coercion

When dealing with route parameters, query strings, and headers the incoming data will be parsed as strings to begin with. From a validation standpoint this can potentially be painful to deal with when dealing with things like Date in javascript. Luckily zod has a built in coercion method attached to its primitive data types to solve this!

convert a route parameter to a number:

router.register({
  path: '/users/:id',
  method: 'get',
  handler: (ctx) => {
    console.log(typeof ctx.request.params.id);
    // 'number'
  },
  validate: {
    params: z.object({ id: z.coerce.number() }),
  },
});

Dealing with dates

As mentioned above type coercion can be very useful in a lot of situations, especially when dealing with dates. Since Date cannot be passed directly into JSON we must convert both the data received and the data being sent back to the client. Avoid using z.date() in your schemas as these will result in validation errors. Instead use z.coerce.date() for input data, and z.string() (or your choice of primitive data-type) for output.

router.register({
  path: '/date',
  method: 'post',
  handler: (ctx) => {
    const { date } = ctx.request.body;
    console.log(date instanceof Date);
    // true
    ctx.body = {
      date: date.toISOString(),
    };
  },
  validate: {
    body: z.object({ date: z.coerce.date() }), // converts received string or number into date object
    response: z.object({ date: z.string() }),
  },
});

Dealing with files

koa-zod-router uses formidable for any requests received with the Content-Type header set to multipart/*.

This functionality is disabled by default, to enable this functionality create an instance of zodRouter and pass in { zodRouter: { enableMultipart: true } } as your config. Then to validate files utilize the helper function zFile.

import zodRouter, { zFile } from 'koa-zod-router';

const fileRouter = zodRouter({ zodRouter: { enableMultipart: true } });

fileRouter.register({
  path: '/uploads',
  method: 'post',
  handler: (ctx) => {
    const { file_one, multiple_files } = ctx.request.files;
    //...
  },
  validate: {
    body: z.object({ hello: z.string() }),
    files: z.object({
      file_one: zFile(),
      multiple_files: z.array(zFile()).or(zFile()),
    }),
  },
});