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08 — Proxy passthrough ​

Mock the routes you're building; forward everything else verbatim to a real backend.

Run this chapter in 30 seconds

  1. Open in StackBlitz → — full Node sandbox in your browser, no install.
  2. Wait for npm install to finish, then in the Terminal tab run:
    npx tsx examples/08-proxy/server.ts
  3. Paste any request from the Try it section below into the Terminal (use curl — the StackBlitz preview port is forwarded).

Concept ​

proxy.target is the upstream URL. When a request doesn't match any endpoint (or the matching endpoint is disabled), mockr forwards it: same method, path, query, body, and headers. Cookies on the response have Domain= and Secure stripped so they stick on localhost.

Toggle at runtime: server.enableProxy() / disableProxy() / setProxyTarget(url).

Code ​

ts
import { mockr, handler } from '@yoyo-org/mockr';

const TARGET = process.env.PROXY_TARGET || 'https://jsonplaceholder.typicode.com';

mockr({
  port: 3008,
  proxy: { target: TARGET },
  endpoints: [
    // mock the routes you're working on
    { url: '/api/feature-flags', data: { darkMode: true, betaSearch: true } },
    {
      url: '/api/users/me',
      handler: handler({
        fn: () => ({ body: { id: 42, name: 'Dev User', role: 'admin' } }),
      }),
    },
  ],
});

Try it ​

Open in StackBlitz → — paste each curl into the StackBlitz Terminal once npx tsx examples/08-proxy/server.ts is running.

bash
# mocked
curl -s http://localhost:3008/api/feature-flags
curl -s http://localhost:3008/api/users/me

# proxied — passthrough to jsonplaceholder
curl -s http://localhost:3008/posts/1
curl -s 'http://localhost:3008/posts?userId=1'

The console tags each line:

  mock  GET    200 /api/feature-flags  3ms
  mock  GET    200 /api/users/me       1ms
   ->   GET    200 /posts/1            142ms

What's next ​

Forward inside a handler and mutate the response before returning → 09 — ctx.forward().

MIT License

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