实现方式
一、github/fetch#20

var p = Promise.race([
  fetch('/resource-that-may-take-a-while'),
  new Promise(function (resolve, reject) {
    setTimeout(() => reject(new Error('request timeout')), 5000)
  })
])
p.then(response => console.log(response))
p.catch(error => console.log(error))

二、github/fetch#20

var req = new Request(url, option);
req.fetch().then((res) => {
  console.log(res.status);
}).catch((err) => {
  console.error(err); // this will also happen in `abort()` request
});

// timeout a request
setTimeout(function() {
  req.abort(); // reject the fetching process
}, 1000);

三、github/fetch#20

const oldfetch = fetch;
fetch = function(input, opts) {
    return new Promise((resolve, reject) => {
        setTimeout(reject, opts.deadline);
        oldfetch(input, opts).then(resolve, reject);
    });
}