使用fetch代替ajax請求 post傳遞方式

let postData = {a:'b'};
fetch('http://data.xxx.com/Admin/Login/login', {
  method: 'POST',
  mode: 'cors',
  credentials: 'include',
  headers: {
    'Content-Type': 'application/x-www-form-urlencoded'
  },
  body: JSON.stringify(postData)
}).then(function(response) {
  console.log(response);
});