middleware

[chiyan-lin]

// 中间件的实现

function App () {
  if (!(this instanceof App)) { return new App() }
  this.init()
}
App.prototype = {
  constructor: App,
  init: function () {
    this.request = { // 模拟的request
      requestLine: 'POST /iven_ HTTP/1.1',
      headers: 'Host:www.baidu.com\r\nCookie:BAIDUID=E063E9B2690116090FE24E01ACDDF4AD:FG=1;BD_HOME=0',
      requestBody: 'key1=value1&key2=value2&key3=value3'
    }
    this.response = {} // 模拟的response
    this.chain = [] // 存放中间件的一个数组
    this.index = 0 // 当前执行的中间件在chain中的位置
  },
  use: function (handle) { // 这里默认 handle 是函数，并且这里不做判断
    this.chain.push(handle)
  },
  next: function () { // 当调用next时执行index所指向的中间件
    if (this.index >= this.chain.length) { return }
    let middleware = this.chain[this.index]
    this.index++
    middleware(this.request, this.response, this.next.bind(this))
  }
}