json-server-reset: Middleware for Data Reset and Merge

Common errors

• TypeError: Cannot read properties of undefined (reading 'db')

  cause The `server.db` property, which the `json-server-reset` middleware expects to find, has not been assigned the `json-server` router's database instance.
  fix After creating your `jsonServer.router`, add `server.db = router.db;` before applying the router middleware.

• Error: reset requires a POST request with JSON body

  cause The `json-server-reset` middleware received a request to the `/reset` or `/merge` endpoint without a valid JSON body, or with an incorrect HTTP method (e.g., GET).
  fix Ensure you are sending a `POST` request to `/reset` or `/merge` and that the request body is valid JSON. Use tools like `httpie` with `key:=value` syntax or `curl -X POST -H "Content-Type: application/json" -d '{"todos":[]}'`.

Warnings

• gotcha The `json-server-reset` middleware must be placed *before* the `jsonServer.router` middleware in your Express application chain. It also requires the `body-parser` middleware to be active to parse incoming JSON payloads for the reset operation.
  Fix: Ensure `server.use(reset)` comes before `server.use(router)`. If not using `jsonServer.defaults({ bodyParser: true })`, manually add `server.use(express.json())` and `server.use(express.urlencoded({ extended: true }))` before `server.use(reset)`.
• gotcha When integrating `json-server-reset` into a custom server setup, you must explicitly assign the `json-server` router's database instance to `server.db` for the reset middleware to function correctly.
  Fix: After initializing `const router = jsonServer.router(dataFilename);`, add `server.db = router.db;` before `server.use(router);`.
• gotcha The package currently uses CommonJS `require` for its main entry points and explicit paths for sub-modules like `merge` and `init-reset`. Attempting to use ESM `import` statements directly might fail depending on your build configuration or Node.js module resolution setup.
  Fix: Use `const reset = require('json-server-reset');` for the main middleware. For `merge` and `init-reset`, use `require('json-server-reset/src/merge')` and `require('json-server-reset/src/init-reset')` respectively.

Install

• npm install json-server-reset npm
• yarn add json-server-reset yarn
• pnpm add json-server-reset pnpm

Imports

• reset
  wrong:

  import reset from 'json-server-reset';

  correct:

  const reset = require('json-server-reset');

  Primarily used in CommonJS style within Node.js servers. The package does not explicitly provide an ESM export for the main middleware, so `require` is the safest option.
• mergeMiddleware
  wrong:

  import { merge } from 'json-server-reset';

  correct:

  const mergeMiddleware = require('json-server-reset/src/merge');

  The 'merge' functionality is exposed as a separate middleware file within the `src` directory, requiring a direct path. It is not a named export from the main package entry point.
• initJsonServerReset
  wrong:

  import { initReset } from 'json-server-reset';

  correct:

  const initJsonServerReset = require('json-server-reset/src/init-reset');

  For initializing resource clearing on server startup, this helper is exposed from a specific file path. Like `merge`, it's not a direct named export.

Quickstart

Demonstrates setting up a `json-server` instance with `json-server-reset` middleware, allowing API data to be reset via a POST request to `/reset`.

const jsonServer = require('json-server');
const reset = require('json-server-reset');
const path = require('path');
const fs = require('fs');

const dataFilename = path.join(__dirname, 'data.json');
// Create a simple initial data file if it doesn't exist
if (!fs.existsSync(dataFilename)) {
  fs.writeFileSync(dataFilename, JSON.stringify({ todos: [], users: [{ id: 1, name: 'Alice' }] }, null, 2));
}

const server = jsonServer.create();
const router = jsonServer.router(dataFilename);

// json-server-reset requires body-parser, which is included in jsonServer.defaults
server.use(
  jsonServer.defaults({
    static: '.', // optional static server folder
    bodyParser: true,
    readOnly: false,
  })
);

// Attach the reset middleware before the json-server router
// The middleware expects the router's db to be accessible via server.db
server.use(reset);
server.db = router.db;
server.use(router);

const PORT = 3000;
server.listen(PORT, () => {
  console.log(`JSON Server with reset middleware is running on port ${PORT}`);
  console.log(`Try:`);
  console.log(`- GET http://localhost:${PORT}/todos`);
  console.log(`- POST http://localhost:${PORT}/todos text='New Todo'`);
  console.log(`- POST http://localhost:${PORT}/reset todos:=[] (using httpie)`);
  console.log(`- POST http://localhost:${PORT}/reset users:='[{ "id": 2, "name": "Bob" }]' (using httpie)`);
});