Cancel allow to manually interrupt a promise execution.
The promise becomes rejected with a CancellationError.

var xhr, promise;
promise = RSVP.Promise(
  // Resolver function
  function (done, fail) {
    xhr = new XMLHttpRequest();
    xhr.open("GET", url);
    xhr.send();
  },
  // Canceller function
  function () {
    xhr.abort();
  },
)
promise.cancel();