/**
 * 使用方式：
 * 1.引入
 * import XHRReq from "xhr-request-tiny";
 *
 * 2.初始化
 * let req = new XHRReq();
 *
 * 3.Promis风格调用 post/get
 * let data = {
    username: 'wc',
    age: 18
  }

  req.post('/api/role/save', data).then(res => {
    console.log('res:', res)
  }).catch(err => {
    console.log('err:', err)
  })

  req.get('/api/role/get', data).then(res => {
    console.log('res:', res)
  }).catch(err => {
    console.log('err:', err)
  })
 */