js design pattern: what is the chain of responsibility pattern? Introduction to js chain of responsibility model

// orderType: 表示订单类型，1：500 元定金用户；2：200 元定金用户；3：普通购买用户
// pay：表示用户是否已经支付定金，true: 已支付；false：未支付
// stock: 表示当前用于普通购买的手机库存数量，已支付过定金的用户不受此限制

const order = function( orderType, pay, stock ) {
  if ( orderType === 1 ) {
    if ( pay === true ) {
      console.log('500 元定金预购，得到 100 元优惠券')
    } else {
      if (stock > 0) {
        console.log('普通购买，无优惠券')
      } else {
        console.log('库存不够，无法购买')
      }
    }
  } else if ( orderType === 2 ) {
    if ( pay === true ) {
      console.log('200 元定金预购，得到 50 元优惠券')
    } else {
      if (stock > 0) {
        console.log('普通购买，无优惠券')
      } else {
        console.log('库存不够，无法购买')
      }
    }
  } else if ( orderType === 3 ) {
    if (stock > 0) {
        console.log('普通购买，无优惠券')
    } else {
      console.log('库存不够，无法购买')
    }
  }
}

order( 3, true, 500 ) // 普通购买，无优惠券

const order500 = function(orderType, pay, stock) {
  if ( orderType === 1 && pay === true ) {
    console.log('500 元定金预购，得到 100 元优惠券')
  } else {
    order200(orderType, pay, stock)
  }
}

const order200 = function(orderType, pay, stock) {
  if ( orderType === 2 && pay === true ) {
    console.log('200 元定金预购，得到 50 元优惠券')
  } else {
    orderCommon(orderType, pay, stock)
  }
}

const orderCommon = function(orderType, pay, stock) {
  if (orderType === 3 && stock > 0) {
    console.log('普通购买，无优惠券')
  } else {
    console.log('库存不够，无法购买')
  }
}

order500( 3, true, 500 ) // 普通购买，无优惠券

// 业务代码
const order500 = function(orderType, pay, stock) {
  if ( orderType === 1 && pay === true ) {
    console.log('500 元定金预购，得到 100 元优惠券')
  } else {
    return 'nextSuccess'
  }
}

const order200 = function(orderType, pay, stock) {
  if ( orderType === 2 && pay === true ) {
    console.log('200 元定金预购，得到 50 元优惠券')
  } else {
    return 'nextSuccess'
  }
}

const orderCommon = function(orderType, pay, stock) {
  if (orderType === 3 && stock > 0) {
    console.log('普通购买，无优惠券')
  } else {
    console.log('库存不够，无法购买')
  }
}

// 链路代码
const chain = function(fn) {
  this.fn = fn
  this.sucessor = null
}

chain.prototype.setNext = function(sucessor) {
  this.sucessor = sucessor
}

chain.prototype.init = function() {
  const result = this.fn.apply(this, arguments)
  if (result === 'nextSuccess') {
    this.sucessor.init.apply(this.sucessor, arguments)
  }
}

const order500New = new chain(order500)
const order200New = new chain(order200)
const orderCommonNew = new chain(orderCommon)

order500New.setNext(order200New)
order200New.setNext(orderCommonNew)

order500New.init( 3, true, 500 ) // 普通购买，无优惠券

// 业务代码
const order500 = function(orderType, pay, stock) {
  if ( orderType === 1 && pay === true ) {
    console.log('500 元定金预购，得到 100 元优惠券')
  } else {
    return 'nextSuccess'
  }
}

const order200 = function(orderType, pay, stock) {
  if ( orderType === 2 && pay === true ) {
    console.log('200 元定金预购，得到 50 元优惠券')
  } else {
    return 'nextSuccess'
  }
}

const orderCommon = function(orderType, pay, stock) {
  if (orderType === 3 && stock > 0) {
    console.log('普通购买，无优惠券')
  } else {
    console.log('库存不够，无法购买')
  }
}

// 链路代码
Function.prototype.after = function(fn) {
  const self = this
  return function() {
    const result = self.apply(self, arguments)
    if (result === 'nextSuccess') {
      return fn.apply(self, arguments) // 这里 return 别忘记了~
    }
  }
}

const order = order500.after(order200).after(orderCommon)

order( 3, true, 500 ) // 普通购买，无优惠券