Fetch Api With Es6 Class

iFetch.js

class fetchApi {
  // method = "GET";
  defaultConfig = {
    method: "GET", // *GET, POST, PUT, DELETE, etc.
    mode: "*same-origin", // no-cors, cors, *same-origin
    cache: "no-cache", // *default, no-cache, reload, force-cache, only-if-cached
    credentials: "*same-origin", // include, *same-origin, omit
    headers: {
      "Content-Type": "application/json",
      Accept: "application/json"
    },
    redirect: "follow", // manual, *follow, error
    referrer: "no-referrer" // no-referrer, *client
  };
  setConfig(defaultConfig) {
    this.defaultConfig = Object.assign({}, this.defaultConfig, defaultConfig);
    return this;
  }
  post(url, data = {}, config = {}) {
    this.defaultConfig.method = "POST";
    let headers = new Headers({
      ...this.defaultConfig,
      ...config,
      body: objectToFormData(data)
    });
    return fetch(new Request(url, headers)).then(async res => {
      let returnObj = {
        statusText: res.statusText,
        status: res.status,
        ok: res.ok,
        type: res.type,
        trailer: res.trailer,
        url: res.url,
        data: await res.json()
      };
      return returnObj;
    });
  }
  put(url, data = {}, config = {}) {
    this.defaultConfig.method = "PUT";
    let headers = new Headers({
      ...this.defaultConfig,
      ...config,
      body: objectToFormData(data)
    });
    return fetch(new Request(url, headers)).then(async res => {
      let returnObj = {
        statusText: res.statusText,
        status: res.status,
        ok: res.ok,
        type: res.type,
        trailer: res.trailer,
        url: res.url,
        data: await res.json()
      };
      return returnObj;
    });
  }
  delete(url, data = {}, config = {}) {
    this.defaultConfig.method = "DELETE";
    let headers = new Headers({
      ...this.defaultConfig,
      ...config,
      body: objectToFormData(data)
    });
    return fetch(new Request(url, headers)).then(async res => {
      let returnObj = {
        statusText: res.statusText,
        status: res.status,
        ok: res.ok,
        type: res.type,
        trailer: res.trailer,
        url: res.url,
        data: await res.json()
      };
      return returnObj;
    });
  }
  get(url, data = {}, config = {}) {
    this.defaultConfig.method = "GET";
    let headers = new Headers({
      ...this.defaultConfig,
      headers: { "Content-Type": "application/x-www-form-urlencoded" },
      ...config,
      body: new URLSearchParams(data)
    });
    return fetch(new Request(url, headers)).then(async res => {
      let returnObj = {
        statusText: res.statusText,
        status: res.status,
        ok: res.ok,
        type: res.type,
        trailer: res.trailer,
        url: res.url,
        data: await res.json()
      };
      return returnObj;
    });
  }
}
const iFetch = new fetchApi();

//examples
    iFetch.get("https://api.ipify.org?format=json").then(a => {
      console.log("a", a, a.data);
    });
    iFetch
      .post("https://api.github.com/repos/vmg/redcarpet/issues?state=closed")
      .then(a => {
        console.log("a", a, a.data);
      });