function request(url, callback) {  fetch(url, {mode: 'cors', credentials: 'include', headers: new Headers({ 'X-Requested-With': 'XMLHttpRequest' })})  .then(response => response.text())  .then(text => {    console.log(url);    console.log(text);    callback(text);  })  .catch((e) => console.log(e));}var iterator = null;function getData(src){  request(src, function(response){    iterator.next(JSON.parse(response));  })}function getTpl(src){  request(src, function(response){    iterator.next(response);  });}// 同步任務function render(data, tpl){  for(var i in data) {    tpl = tpl.replace("${"+i+"}", data[i]);  }  return tpl;}// 主邏輯var getArticles = function* (src){  console.log('begin')  var data = yield getData(src)  var tpl = yield getTpl(data.tpl)  var res = render(data, tpl)  console.log(res)}iterator = getArticles('data.json')// 開始執行iterator.next()// 異步任務模型