nextjs-typesafe-api-routes

This is a Type-Safe solution for Next.js API Routes.There was a risk of making some mistakes between API Routes and Client.By using this solution, it is possible to build a type-safe environment by linking both type inferences.

1.Define API Routes Handlers

First, define API Routes handler with ApiHandler.As defined below, it is necessary to divide the handler for each request method.

import type { ApiHandler } from "@/types/pages/api";

export type GetHandler = ApiHandler<{ name: string }, {}, { message: string }>;
const getHandler: GetHandler = (req, res) => {
  if (!req.query.name) {
    res
      .status(400)
      .json({ error: { httpStatus: 400, message: "Invalid Request" } });
    return;
  }
  res.status(200).json({ data: { message: `hello ${req.query.name}` } });
};

const handler: ApiHandler = (req, res) => {
  switch (req.method) {
    case "GET":
      getHandler(req, res);
      break;
    default:
      res
        .status(405)
        .json({ error: { httpStatus: 405, message: "Method Not Allowed" } });
  }
};
export default handler;

Generics for ApiHandler, expect three Generics ResBody, ReqQuery, ReqBody in order.

2.Generate Type Definitions

Run below npm scripts, then generate api types into src/types/pages/api/**/*.

$ npm run gen:apitype

3.Check Type Inference in Client

useApiData provides type inference from the specified string such as "/api/greet".

const { data } = useApiData("/api/greet", { query: { name: "user" } });