javascript-di-container.js

export default class Container {
  constructor(builder) {
    this.services = new Map();
    if (builder !== undefined) {
      Object.keys(builder).forEach(name => this.register(name, builder[name]));
    }
  }

  /**
   * Register a service
   * 
   * @param name 
   * @param sig service signature
   */
  register(name, sig) {
    this.services.set(name, {sig, instance: null})
  }

  /**
   * Get a service
   * 
   * @param name 
   */
  get(name): any {
    const service = this.services.get(name)
    if (service.instance !== null) {
      return service.instance;
    }

    const instance = service.sig.constructor(this);
    this.services.set(name, {sig: service.sig, instance})

    return instance;
  }

  /**
   * Boot those services that need to be booted
   */
  public boot() {
    const bootP = [];
    this.services.forEach((service, name) => {
      const sig = service.sig;
      if (sig.tags !== undefined && sig.tags.includes('boot')) {
        bootP.push(this.get(name).boot(this));
      }
    })
    
    return bootP;
  }
}