Cancelable Promise Sequence

cancelableSequence.js

var promises = [promise1, promise2, promise3];

// Now you can actually call a cancel interface without affecting the state of the promises.
var cancelable = cancelableSenquence(promises);


function cancelableSequence(promises) {
  var cancelled = false;

  var cancelable = promises.reduce(function(prev, curr) {
    return prev.then(function() {
      if (!cancelled) {
        return curr;
      }
    }, function(err) {
      cancelled = true;
      return err;
    })
  }, Promise.resolve());
  
  cancelable.cancel = function() {
    cancelled = true;
  };
  
  return cancelable;
}