What does the following module augmentation achieve? // In express.d.ts import ‘express’; declare module ‘express’ { interface Request { user?: { id: string }; } }

Question

TypeScript Professional — Hard

What does the following module augmentation achieve? // In express.d.ts import ‘express’; declare module ‘express’ { interface Request { user?: { id: string }; } }

Accepted Answer

The module augmentation in the code snippet adds a 'user' property to Express's Request interface through declaration merging. This allows extending the existing type without altering the original express package's source types.