How to cancel timeout inside of Javascript Promise?

I'm toying with promises in JavaScript and tried to promisify setTimeout function:

function timeout(ms) {
  return new Promise(function(resolve, reject) {
    setTimeout(function() {
      resolve('timeout done');
    }, ms);
  }); 
}

var myPromise=timeout(3000); 

myPromise.then(function(result) { 
  console.log(result); // timeout done
})

Fairly straightforward but I was wondering how would I go about canceling my timeout before the promise resolves. timeout returns Promise object hence I loose access to value that setTimeout returns and cannot cancel timeout via clearTimeout. What woud be the best way to do it?

BTW there is no real purpose for this, I just wonder how this would be approached. Also I plunked it here http://plnkr.co/edit/NXFjs1dXWVFNEOeCV1BA?p=preview