使用Promise封装fetch和ajax请求

• $fetch请求方法支持fetch和ajax的get,post 等方法，对异步请求对象的封装，增加了手动取消请求的能力。

今天对这部分代码进行测试时发现用ajax发送请求时会报一个promise错误，随后测试发现有部份代码写的有问题。随更新。

/**
 * @Author Visupervi
 * @Date 2019/12/16 10:55
 * @Name fetch 封装
 * @Param
 * @Return
 * @Description 对fetch封装，包含get,post ajax的post请求
 */
export default $fetch = async (url = "", data = {}, type = "GET", method = "fetch") => {
  const time = 3000;
  if (type.toLocaleLowerCase() === "get") {
    let str = "";
    Object.keys(data).map((item, index) => {
      str += item + '=' + data[item] + '&';
    });
    if (str !== "") {
      str = str.substr(0, str.lastIndexOf("&"));
      url = url + "?" + str;
    }
  }

  if (window.fetch && method === "fetch") {
    let requestConfig = {
      credentials: 'include',
      method: type,
      headers: {
        'Accept': 'application/json',
        'Content-Type': 'application/json'
      },
      mode: "cors",
      cache: "force-cache"
    };
    //fetch中的post 的请求
    if (type.toLocaleLowerCase() === "post") {
      Object.defineProperty(requestConfig, 'body', {
        value: JSON.stringify(data)
      })
    }

    try {
      const {body} = requestConfig;
      const controller = new AbortController();
      let timerId = null;
      const {signal} = controller;
      timerId = setTimeout(() => controller.abort(), time)
      requestConfig = {
          ...requestConfig,
          body,
          signal
      }
      const response = await fetch(url, requestConfig);
      return await response.json();
    } catch (e) {
      throw new Error(e)
    }
  } else {
    return new Promise((resolve, reject) => {
      let reqObj = !window.XMLHttpRequest ? new ActiveXObject : new XMLHttpRequest();
      let sendData = "";

      //ajax中的post请求
      if (type.toLowerCase() === "post") {
        sendData = JSON.stringify(data)
      }
      reqObj.open(type, url, true);
      reqObj.timeout = time;
      reqObj.setRequestHeader("Content-type", "application/json");
      reqObj.send(sendData);

      reqObj.onreadystatechange = () => {
        if (reqObj.readyState !== 4) return;
        if (reqObj.status >= 200 && reqObj.status < 400) {
          resolve(JSON.parse(reqObj.response);
        } else {
          reject(reqObj.response)
        }
      }
    })
  }

}