递归执行Generator

  function ajax (url) {
    return new Promise(function (resolve, reject) {
      let xhr = new XMLHttpRequest()
      xhr.open('GET', url)
      xhr.responseType = 'json'
      xhr.onload = function () {
        if (this.status + '' === '200') {
          resolve(this.response)
          console.log(this.response)
        } else {
          reject(new Error(this.responseText))
          console.log(this.responseText)
        }
      }
      xhr.send()
    })
  }
function * main () {
  try {
    const users = yield ajax('/ajaxTest.js')
    console.log(users)
      const post = yield ajax('/ajaxPost.js')
    console.log(post)
  }catch (e) {
    console.log(e)
  }
}
function coo (generator) {
  const g = generator()
  function handleResult (data) {
  if (data.done) return
  data.value.then(result => {
    handleResult(g.next(data))
  }, function (error) {
    g.throw(error)
  })
}
handleResult(g.next())
}
coo(main)