Node Config

A utility library designed to simplify configuration management in TypeScript and Node.js applications. This library includes powerful decorators, validation features, and utils to effortlessly integrate and validate application configurations.

Features

1. Simplified Configuration Management

• Define configurations as strongly typed classes with decorators for validation and transformation.
• Centralize configuration logic, making it easy to maintain and extend.

2. Type-Safe Configurations

• The getConfig function ensures type safety by mapping environment variables directly to configuration class properties.
• Automatically parses and validates properties against the defined class structure.

3. Validation with class-validator

• Use decorators like @IsString, @IsEnum, @IsInt, and @IsBoolean to enforce rules on configuration values.
• Validation errors provide meaningful feedback during development or runtime.

4. Dynamic Transformation with class-transformer

• Apply transformations (e.g., converting strings to booleans) seamlessly using decorators like @Transform.

5. Integration with Frameworks

• Built to integrate easily with frameworks like NestJS, enabling configuration classes to power dynamic module setups (e.g., database connections).

6. Environment Variable Handling

• Map environment variables to class properties effortlessly.
• Enforces clean and predictable configuration values from the environment.

7. Dependency injection between config classes

• Define constructor based injections, similiar to Injectables in Nestjs modules
• Synchronized resolve of dependent configurations within one class

8. Reads environment variables from .env files using dotenv

• Out-of-the-box integration with dotenv library for reading environment variables

Installation

yarn

yarn add @codemask-labs/node-config class-validator class-transformer

npm

npm install @codemask-labs/node-config class-validator class-transformer

API

getConfig

declare function getConfig(configClass: ClassType): ConfigInstance

Retrieves and validates an instance of the configuration class.

Parameters

• configClass: The configuration class with @Config and validation decorators applied.

Returns

• An instance of the validated configuration class.

getConfigValue

declare function getConfigValue<T extends ClassType, U>(configClass: T, getter: (config: T) => U): U

Retrieves and validates an instance of the configuration class, and passed through a getter to return a value.

Parameters

• configClass: The configuration class with @Config and validation decorators applied.
• getter: The getter function that runs synchronously on

Returns

• An value constructed by of the validated configuration class.

Env decorator

declare function Env(propertyName: string): MethodDecorator

Maps process environment to class property by name, useful when you need to validate or transform environment variable and map it to other casing.

Parameters

• propertyName: The usually process.env key to a value

Retruns

• An class property decorator that can be used within a @Config decorated class.

Usage

Define a Configuration Class

Use decorators to define and validate configuration properties.

import { Transform } from 'class-transformer';
import { IsBoolean, IsEnum, IsInt, IsString, MaxLength } from 'class-validator';
import { Config } from '@codemask-labs/node-config';
import { TypeormConnection } from 'example/enums';

@Config()
export class TypeormConfig {
    @IsEnum(TypeormConnection)
    readonly TYPEORM_CONNECTION: TypeormConnection;

    @IsString()
    readonly TYPEORM_HOST: string;

    @IsInt()
    readonly TYPEORM_PORT: number;

    @IsString()
    readonly TYPEORM_DATABASE: string;

    @IsString()
    @MaxLength(100)
    readonly TYPEORM_USERNAME: string;

    @IsString()
    readonly TYPEORM_PASSWORD: string;

    @IsBoolean()
    readonly TYPEORM_LOGGING: boolean;

    @IsBoolean()
    @Transform(({ value }) => value === 'true')
    readonly TYPEORM_DEBUG: boolean;
}

Access Configuration in Code

Use the getConfig function to access and validate the configuration class.

import { getConfig } from '@codemask-labs/node-config';
import { TypeormConfig } from 'example/config';

const config = getConfig(TypeormConfig);

console.log(config.TYPEORM_HOST); // Outputs the validated host value

Example Integration with NestJS

import { Module } from '@nestjs/common';
import { TypeOrmModule } from '@nestjs/typeorm';
import { getConfig } from '@codemask-labs/node-config';
import { TypeormConfig } from 'example/config';

@Module({
    imports: [
        TypeOrmModule.forRootAsync({
            useFactory: () => {
                const {
                    TYPEORM_CONNECTION,
                    TYPEORM_HOST,
                    TYPEORM_PORT,
                    TYPEORM_USERNAME,
                    TYPEORM_PASSWORD,
                    TYPEORM_DATABASE,
                    TYPEORM_LOGGING,
                } = getConfig(TypeormConfig);

                return {
                    type: TYPEORM_CONNECTION,
                    host: TYPEORM_HOST,
                    port: TYPEORM_PORT,
                    username: TYPEORM_USERNAME,
                    password: TYPEORM_PASSWORD,
                    database: TYPEORM_DATABASE,
                    entities: Object.values({}),
                    migrations: Object.values({}),
                    synchronize: false,
                    migrationsRun: true,
                    autoLoadEntities: true,
                    logging: TYPEORM_LOGGING ? 'all' : undefined,
                };
            },
        }),
    ],
})
export class UsersModule {}

Injecting other configurations to a single class

import { NodeEnv } from 'example/enums';

export class NodeConfig {
    @IsEnum(NodeEnv)
    @Env('NODE_ENV') // reads it from `process.env`, and maps it to your class property `environment`
    readonly environment: NodeEnv;
}

import { NodeConfig } from 'example/config';

export class TypeormConfig {
    constructor(readonly nodeConfig: NodeConfig) {}
}

import { TypeormConfig } from 'example/config';

const config = getConfig(TypeormConfig); // Transforms and validates `NodeConfig` as dependency, then transforms and validates `TypeormConfig`, returns instance.

console.log(config.nodeConfig.environment); // Outputs the validated and transformed value of `NODE_ENV`

License

This project is licensed under the MIT License.