typescript 50 lines · 6 steps

Validated, typed config in NestJS

A NestJS module validates environment variables at startup with Joi and exposes them through a typed, injectable service.

Explained by highlit

NestJS Intermediate configuration validation dependency-injection environment-variables fail-fast

1import { Module, Injectable } from '@nestjs/common';
2import { ConfigModule, ConfigService } from '@nestjs/config';
3import * as Joi from 'joi';
4 
5const validationSchema = Joi.object({
6  NODE_ENV: Joi.string().valid('development', 'production', 'test').default('development'),
7  PORT: Joi.number().default(3000),
8  DATABASE_URL: Joi.string().uri().required(),
9  JWT_SECRET: Joi.string().min(32).required(),
10  JWT_EXPIRES_IN: Joi.string().default('3600s'),
11});
12 
13@Module({
14  imports: [
15    ConfigModule.forRoot({
16      isGlobal: true,
17      cache: true,
18      envFilePath: [`.env.${process.env.NODE_ENV ?? 'development'}`, '.env'],
19      validationSchema,
20      validationOptions: { abortEarly: false },
21    }),
22  ],
23  providers: [AppConfigService],
24  exports: [AppConfigService],
25})
26export class AppConfigModule {}
27 
28@Injectable()
29export class AppConfigService {
30  constructor(private readonly config: ConfigService) {}
31 
32  get isProduction(): boolean {
33    return this.config.getOrThrow<string>('NODE_ENV') === 'production';
34  }
35 
36  get port(): number {
37    return this.config.getOrThrow<number>('PORT');
38  }
39 
40  get databaseUrl(): string {
41    return this.config.getOrThrow<string>('DATABASE_URL');
42  }
43 
44  get jwt(): { secret: string; expiresIn: string } {
45    return {
46      secret: this.config.getOrThrow<string>('JWT_SECRET'),
47      expiresIn: this.config.getOrThrow<string>('JWT_EXPIRES_IN'),
48    };
49  }
50}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Validating env vars at boot turns silent misconfiguration into a loud, immediate failure.
2Wrapping ConfigService in a typed service gives the rest of the app safe, autocompleted access to settings.
3Marking the config module global lets every feature read configuration without re-importing it.

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