@lurenjs/config

This a TypeScript library is to help you create a configuration class that values are injected from environment variables or files.

Prerequisites

experimentalDecorators, emitDecoratorMetadata compilation options should be enabled in your tsconfig.json file.

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

Installation

yarn

$ yarn add @lurenjs/config reflect-metadata

npm

$ npm i -S @lurenjs/config reflect-metadata

Usage

Inject config from ENV

The configuration class should be decorator with Configuration, each property that you want to inject should be decorated with InjectEnv. Values will be injected when instance is created.

@Configuration()
class Foo {
  @InjectEnv('HOST', { default: 'localhost' })
  public host: string;
  @InjectEnv('PORT', {
    transform: (val) => Number.parseInt(val, 10),
  })
  public port: number;
  @InjectEnv('DATABASE', { description: 'database name' })
  public database: string;
}

/**
 * ENV
 *
 * PORT=1234
 * DATABASE=test
 *
 **/

const foo = new Foo()
console.log(foo)
/**
 *  Foo { host: 'localhost', port: 1234, database: 'test' }
 ** /

Notice:For env variable injection, Configuration decorator is not required, but then value will be set on the prototype, that means fields won't be listed in Object.keys() or Object.getOwnProperites().

import { InjectEnv } from './inject-env';

class Foo {
  @InjectEnv('HOST', { default: 'localhost' })
  host: string;
  @InjectEnv('PORT', {
    transform: (val) => Number(val),
  })
  port: number;
  @InjectEnv('DATABASE', { description: 'database name' })
  database: string;
}

const foo = new Foo();
console.log(foo);
/* Foo {} */

console.log(foo.host, foo.port, foo.database);
/* localhost 1234 db_name */

static fields can be injected too.

import { InjectEnv } from './inject-env';

class Foo {
  @InjectEnv('HOST', { default: 'localhost' })
  static host: string;
  @InjectEnv('PORT', {
    transform: (val) => Number(val),
  })
  static port: number;
  @InjectEnv('DATABASE', { description: 'database name' })
  static database: string;
}

/**
 * ENV
 *
 * HOST=localhost
 * PORT=1234
 * DATABASE= db_name
 *
 **/

console.log(Foo)
/**
 * [class Foo] { host: 'localhost', port: 1234, database: 'db_name' }
 ** /

Config source can be an file, json and yaml format is supported, yaml is the default format. Then base filepath cwd(current work directory).

 @Configuration({ filepath: './test/config.yml' })
    class Bar {
      @InjectProp()
      zee: number;

      @InjectProp()
      foo: string;

      @InjectProp({ transform: (val) => Number(val) })
      ordinal: number;
    }
    const bar = new Bar();

/**
 * ./test/config.yml
 *
 * foo: bar
 * ordinal: "1"
 * zee: 1
 *
 **/

const bar = new Bar()
/**
 * Bar { zee: 1, foo: 'bar', ordinal: 1 }
 ** /