var Light = function () {
  this.state = 'off' // 给电灯设置初始状态off
  this.button = null // 电灯开关按钮
}

Light.prototype.init = function () {
  var button = document.createElement('button')
  var self = this
  
  button.innerHTML = '开关'
  this.button = document.body.appendChild(button)
  this.button.onclick = function () {
    self.buttonWasPressed()
  }
}

Light.prototype.buttonWasPressed = function () {
  if (this.state === 'off') {
    console.log('开灯')
    this.state = 'on'
  } else if (this.state === 'on') {
    console.log('关灯')
    this.state = 'off'
  }
}

var light = new Light()
light.init()

Light.prototype.buttonWasPressed = function () {
  if (this.state === 'off') {
    console.log('弱光')
    this.state = 'weakLight'
  } else if (this.state === 'weakLight') {
    console.log('强光')
    this.state = 'strongLight'
  } else if (this.state === 'strongLight') {
    console.log('关灯')
    this.state = 'off'
  }
}

// OffLightState
var OffLightState = function (light) {
  this.light = light
}

OffLightState.prototype.buttonWasPressed = function () {
  console.log('弱光') // 切换时对应的行为
  this.light.setState(this.light.weakLightState) // 状态切换到weakLightState
}

// WeakLightState
var WeakLightState = function (light) {
  this.light = light
}

WeakLightState.prototype.buttonWasPressed = function () {
  console.log('强光') // 切换时对应的行为
  this.light.setState(this.light.strongLightState) // 状态切换到strongLightState
}

// StrongLightState
var StrongLightState = function (light) {
  this.light = light
}

StrongLightState.prototype.buttonWasPressed = function () {
  console.log('关灯') // 切换时对应的行为
  this.light.setState(this.light.offLightState) // 状态切换到offLightState
}

// 改写Light类
var Light = function () {
  this.offLightState = new OffLightState(this)
  this.weakLightState = new WeakLightState(this)
  this.strongLightState = new StrongLightState(this)
  this.button = null
}

Light.prototype.init = function () {
  var button = document.createElement('button')
  var self = this
  
  button.innerHTML = '开关'
  this.currState = this.offLightState
  this.button = document.body.appendChild(button)
  this.button.onclick = function () {
    self.currState.buttonWasPressed()
  }
}

Light.prototype.setState = function (newState) {
  this.currState = newState
}

var light = new Light()
light.init()

// SuperStrongLightState
var SuperStrongLightState = function (light) {
  this.light = light
}

SuperStrongLightState.prototype.buttonWasPressed = function () {
  console.log('关灯')
  this.light.setState(this.light.offLightState) // 状态切换到offLightState
}

// 修改StrongLightState
var StrongLightState = function (light) {
  this.light = light
}

StrongLightState.prototype.buttonWasPressed = function () {
  console.log('超强光') // 切换时对应的行为
  this.light.setState(this.light.superStrongLightState) // 状态切换到offLightState
}

// 改写Light类
var Light = function () {
  this.offLightState = new OffLightState(this)
  this.weakLightState = new WeakLightState(this)
  this.strongLightState = new StrongLightState(this)
  this.superStrongLightState = new SuperStrongLightState(this)
  this.button = null
}

var State = function () {}

State.prototype.buttonWasPressed = function () {
  throw new Error('父类的buttonWasPressed方法必须被重写')
}

var SuperStrongLightState = function (light) {
  this.light = light
}

SuperStrongLightState.prototype = new State()

SuperStrongLightState.prototype.buttonWasPressed = function () {
  console.log('关灯')
  this.light.setState(this.light.offLightState) // 状态切换到offLightState
}