fetch("http://blog.parryqiu.com").then(function(response){console.log(response)})

 self.fetch = function (input, init) {
  return new Promise(function (resolve, reject) {
   var request = new Request(input, init)
   var xhr = new XMLHttpRequest()
   xhr.onload = function () {
    var options = {
     status: xhr.status,
     statusText: xhr.statusText,
     headers: parseHeaders(xhr.getAllResponseHeaders() || '')
    }
    options.url = 'responseURL' in xhr ? xhr.responseURL : options.headers.get('X-Request-URL')
    var body = 'response' in xhr ? xhr.response : xhr.responseText
    resolve(new Response(body, options))
   }
   xhr.onerror = function () {
    reject(new TypeError('Network request failed'))
   }
   xhr.ontimeout = function () {
    reject(new TypeError('Network request failed888888888888'))
   }
   xhr.open(request.method, request.url, true)
   if (request.credentials === 'include') {
    xhr.withCredentials = true
   }
   if ('responseType' in xhr && support.blob) {
    xhr.responseType = 'blob'
   }
   request.headers.forEach(function (value, name) {
    xhr.setRequestHeader(name, value)
   })
   xhr.send(typeof request._bodyInit === 'undefined' ? null : request._bodyInit)
  })
 }

 _timeout_fetch(fetch_promise, timeout = 15000) {
  let timeout_promise = new Promise(function (resolve, reject) {
   setTimeout(() => {
    reject('timeout promise');
   }, timeout)
  });
  return Promise.race([
   fetch_promise,
   timeout_promise
  ]);
 }

 this._timeout_fetch(
    fetch(url, requestParams)
     .then(response => response.json())
     .then(responseData => {
      resolve(responseData);
     })
     .catch(error => {
      reject(error);
     })
   )

 xhr.timeout = init.timeout || 0;

 let requestParams = {
   method: method,
   header: {
    "Content-Type": "application/json;charset=UTF-8",
   },
   timeout: 1000
  };

 self.fetch = function (input, init) {
  var xhr = new XMLHttpRequest()
  let p = new Promise(function (resolve, reject) {
   var request = new Request(input, init)
   // xhr的各种设置，回调等
  })
  p.cancel = () => {
   xhr.abort()
  }
  return p;
 }

  let promise = fetch(url);
  promise.then(res => {
  }).then(res => {
  }).catch(err => {
  })
  promise.cancel() // 取消该网络请求