EventBus - Vanilla JS

EventBus.js

class EventBus {
  registry = new Map()
  constructor() {}

  on(type, handler) {
    const handlers = this.registry.get(type)
    const added = handlers && handlers.push(handler)
    if (!added) {
      this.registry.set(type, [handler])
    }
  }

  off(type, handler) {
    const handlers = this.registry.get(type)
    const handlerIndex = handlers.indexOf(handler)
    if (handlers && handlerIndex > -1) {
      handlers.splice(handlerIndex, 1)
    }
  }

  emit(type, payload) {
    this.registry
      .get(type)
      .slice()
      .map((handler) => handler(payload))
  }
}

test.js

const bus = new EventBus()

function test(p) {
  console.log('test!', payload)
}

bus.on('test', test)
bus.on('test1', (payload) => console.log('test 1!', payload))

bus.off('test', test)

bus.emit('test1')
bus.emit('test')