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

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