Hono middleware for strinfigying BigInt types in responses

tranformJsonResponse.ts

import { createMiddleware } from "hono/factory";
import type {
  InvalidJSONValue,
  JSONValue,
  SimplifyDeepArray,
} from "hono/utils/types";

export const transformJsonResponse = createMiddleware(async (ctx, next) => {
  const originalJson = ctx.json.bind(ctx);
  type JsonFn = (
    obj: JSONValue | SimplifyDeepArray<unknown> | InvalidJSONValue,
    init?: ResponseInit,
  ) => Response;

  (ctx.json as JsonFn) = (
    obj: JSONValue | SimplifyDeepArray<unknown> | InvalidJSONValue,
    init?: ResponseInit,
  ) => {
    const json = JSON.stringify(obj, (_key, value) => {
      if (typeof value === "bigint") return value.toString();
      return value;
    });

    return originalJson(JSON.parse(json), init);
  };

  await next();
});