reqwest怎样获取响应头

登录成功将token通过header传输，怎样获取header中的Authorization？
getResponseHeader提示找不到相关函数

reqwest({
  url: 'http://localhost:8783/user/login',
  method: 'get',
  headers: {
    'Content-Type': 'application/json',
    'Access-Control-Allow-Origin': 'http://localhost:8783/*',
    'Accept': 'application/json',
  },
  type: 'json',
  data: {
    'userName': values.userName,
    'password': values.password
  }
}).then((data) => {
  if (data === 'fail') {
    window.alert('用户名或密码错误');
  } else {

  }
});

var r = reqwest({
    url: url,
    type: 'json',
    method: 'GET',
    contentType: 'application/json',
    headers: getHeaders()
}).then(function(response) {
    console.log(r.request.getResponseHeader('Authorization'));
});