🚦 Define app route handler ─ A basic function to define a new route handler for Next.js 13's app directory

defineAppRouteHandler.ts

type ByteFormatStr = "b" | "gb" | "kb" | "mb" | "pb" | "tb";
type ByteSize = `${number}${ByteFormatStr}`;

interface NextApiConfig {
  api?: {
    bodyParser?:
      | false
      | {
          sizeLimit: ByteSize;
        };
    externalResolver?: boolean;
    responseLimit?: ByteSize;
  };
  runtime?: "edge" | "nodejs";
  regions?: Array<string>;
}

type NextRouteHandler<
  TParams extends Record<string, unknown> = Record<string, unknown>,
  TResponse extends Response = Response
> = (request: Request, params: { params?: TParams }) => TResponse | Promise<TResponse>;

type SupportedHTTPMethods =
  | "DELETE"
  | "GET"
  | "HEAD"
  | "OPTIONS"
  | "PATCH"
  | "POST"
  | "PUT";

type DefineAppRouteHandlerOptions<TParams extends Record<string, unknown>> =
  Record<SupportedHTTPMethods, NextRouteHandler<TParams>> & NextApiConfig;

export function defineAppRouteHandler<
  TParams extends Record<string, unknown> = Record<string, unknown>,
  TOptions extends Partial<DefineAppRouteHandlerOptions<TParams>> = Partial<
    DefineAppRouteHandlerOptions<TParams>
  >
>(options: TOptions): TOptions {
  return options;
}

example.ts

// app/blog/[slug]/route.ts

import { NextResponse } from "next/server";

import { defineAppRouteHandler } from 'path/to/util';

export const { config, GET } = defineAppRouteHandler<{ slug: string }>({
	runtime: 'edge',
	GET: (_req, { params }) => NextResponse.json({
		slug: params?.slug,
	}),
});