Container.js

class Container {
  static get proxyHandler () {
    return {
      get (target, prop) {
        if (prop in target) {
          return Reflect.get(...arguments)
        }

        return target.resolve(prop)
      }
    }
  }

  static getInstance () {
    if (!this.instance) {
      this.instance = new Proxy(new this, this.proxyHandler)
    }

    return this.instance
  }

  constructor () {
    this.bindings = []
    this.instances = []
  }

  singleton (abstract, concrete) {
    this.bindings[abstract] = concrete
  }

  instance (abstract, instance) {
    this.instances[abstract] = instance
  }

  resolve (abstract) {
    if (abstract in this.bindings && !(abstract in this.instances)) {
      this.instances[abstract] = this.bindings[abstract]()
    }

    return this.instances[abstract]
  }
}