nx/docs/react/tutorial/06-proxy.md

Step 6: Proxy

You passed --frontendProject=todos when creating the node application. What did that argument do?

It created a proxy configuration that allows the React application to talk to the API in development.

To see how it works, open workspace.json and find the serve target of the todos app.

{
  "serve": {
    "builder": "@nrwl/web:dev-server",
    "options": {
      "buildTarget": "todos:build",
      "proxyConfig": "apps/todos/proxy.conf.json"
    },
    "configurations": {
      "production": {
        "buildTarget": "todos:build:production"
      }
    }
  }
}

Note the proxyConfig property.

Now open proxy.conf.json:

{
  "/api": {
    "target": "http://localhost:3333",
    "secure": false
  }
}

This configuration tells ng serve to forward all requests starting with /api to the process listening on port 3333.

!!!!! Now run both "ng serve todos" and "ng serve api", open http://localhost:4200. What do you see? !!!!! Todos application is working! 404 in the console Todos are displayed but the Add Todo button doesn't work