Event emitter

emitter.js

export default class Emitter {
  constructor() {
    this.subscriptions = {}
  }

  subscribe(name, cb) {
    if (!Array.isArray(this.subscriptions[name])) {
      this.subscriptions[name] = []
    }
    this.subscriptions[name].push(cb)

    return () => {
      this.subscriptions[name] = this.subscriptions[name].filter(subCb => subCb !== cb)
    }
  }

  emit(name, ...args) {
    if (Array.isArray(this.subscriptions[name])) {
      return this.subscriptions[name].map(cb => cb(...args))
    }

    return []
  }
}