NestJS Basics — Series 3

Preview — 3 of 10 questions

What makes AppModule special?

javascript

const app = await NestFactory.create(AppModule);

AIts file name — Nest looks for app.module.ts by convention

BThe @Root() decorator it carries in addition to @Module()

CNothing about the class itself: it is the root purely because it is the module handed to NestFactory.create(), which then walks its imports to discover every other module

DIt is the only module allowed to declare controllers

Why is this the production start command rather than nest start?

javascript

nest build
node dist/main.js

Anest start cannot read environment variables

Bnest build compiles TypeScript to JavaScript in dist/, and production runs that output directly with Node — nest start is a development wrapper that compiles on the fly and depends on the Nest CLI being installed

Cnode dist/main.js enables clustering automatically, which nest start does not

DThey are identical; nest start is simply the longer form

What breaks if emitDecoratorMetadata is turned off?

javascript

{
  "compilerOptions": {
    "experimentalDecorators": true,
    "emitDecoratorMetadata": true
  }
}

ADependency injection by type stops working: the compiler no longer emits the constructor's parameter types, so Nest has no token to resolve and reports unresolvable dependencies

BDecorators themselves stop being recognised, so @Controller() becomes a syntax error

CNothing at runtime; the flag only affects editor tooling

DRoute paths are no longer registered, though providers still resolve

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