var api1 = 'https://anapioficeandfire.com/api/characters/583'
var api2 = 'https://anapioficeandfire.com/api/characters/584'

function *fetchData () {
  var res = yield request(api1)
  res.json().then(data => {
    console.log(data.name) // Jon Snow
  })
}

function request (url) {
  fetch(url).then(res => {
    it.next(res)
  })
}

var it = fetchData()
it.next()

var api1 = 'https://anapioficeandfire.com/api/characters/583'
var api2 = 'https://anapioficeandfire.com/api/characters/584'

function *fetchData () {
  var res = yield fetch(api1).then(data => fetchData().next(data))
  res.json().then(data => {
    console.log(data.name)
  })
}

fetchData().next()

第一段代码可以正确打印出结果，而第二段代码却不行，想问下为什么，我觉得两段代码并没有区别