Namespaced Config & Hooks

Preview — 3 of 10 questions

You pass a validationSchema (Joi) to ConfigModule.forRoot(). What is the effect at application startup?

javascript

import * as Joi from 'joi';

ConfigModule.forRoot({
  validationSchema: Joi.object({
    NODE_ENV: Joi.string().valid('development', 'production', 'test').required(),
    PORT: Joi.number().default(3000),
    DATABASE_URL: Joi.string().uri().required(),
  }),
  validationOptions: { abortEarly: false },
});

AIt validates the loaded environment variables and throws (aborting boot) if any required value is missing or malformed

BIt silently coerces invalid values to defaults and continues

CIt only validates values the first time ConfigService.get() is called

DIt runs validation on every HTTP request before the route handler

You provide load: [() => ({ database: { host: process.env.DB_HOST } })]. How do you read the host?

javascript

ConfigModule.forRoot({
  load: [() => ({ database: { host: process.env.DB_HOST } })],
});

// Later:
const host = this.config.get<string>('database.host');

Aconfig.get('DB_HOST')

Bconfig.get('database/host')

Cconfig.get('database.host')

Dconfig.get('database').host()

What does the generic in config.get<string>('database.host') actually do?

javascript

// Compile-time type is string, but runtime value is whatever was stored.
const host = this.config.get<string>('database.host');
// If you need a number, parse/validate explicitly:
const port = Number(this.config.get('PORT'));

AIt validates at runtime that the value is a string and throws otherwise

BIt registers the key as required in the validation schema

CIt converts the stored value into a string at runtime

DIt only affects the compile-time return type; no runtime conversion or check happens

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