body(): ArrayBuffer

import http from 'pts/http';

const data = open('./sample/tmp.js');

export default function () {
  const formData = new http.FormData();
  
  formData.append('text', 'text');
  formData.append('file', http.file(data, 'tmp.js'));
  
  // 输出 [object ArrayBuffer]
  console.log(formData.body());
  
  const resp = http.post('http://httpbin.org/post', formData.body(), {
    headers: {'Content-Type': formData.contentType()}
  });
  
  console.log('formData: ', resp.body);
};