Formdata请求配置

transformRequest: [
  function(data) {
    let ret = '';
    for (let it in data) {
      ret += encodeURIComponent(it) + '=' + encodeURIComponent(data[it]) + '&';
    }
    return ret;
  }
],
//设置请求头
headers: {
  'Content-Type': 'application/x-www-form-urlencoded'
}