seerline/clchart

export default class EventEmitter {
  constructor () {
    this.handlers = {}
  }

  emit (event, ...args) {
    if (this.handlers[event]) {
      this.handlers[event].forEach((handler) => handler.apply(this, args))
    }
  }

  emitWithScope (event, scope, ...args) {
    if (this.handlers[event]) {
      this.handlers[event].forEach((handler) => handler.apply(scope, args))
    }
  }

  on (event, callback) {
    if (!this.handlers[event]) {
      this.handlers[event] = []
    }
    this.handlers[event].push(callback)
  }

  once (event, callback) {
    const self = this
    self.on(event, function onetimeCallback () {
      callback.apply(this, arguments)
      self.removeListener(event, onetimeCallback)
    })
  }

  removeListener (event, callback) {
    if (this.handlers[event]) {
      const index = this.handlers[event].indexOf(callback)
      if (index > -1) {
        this.handlers[event].splice(index, 1)
      }
    }
  }

  removeAllListeners (event) {
    this.handlers[event] = undefined
  }
};