rsvp-vs-promise-then.js

gistfile1.js

var rsvp = require('rsvp');

class TestPromiseFromNative extends Promise {
  then(onFulfillment, ...args) {
    return super.then(result => isolate(onFulfillment, result), ...args);
  }
}

class TestPromiseFromRSVP extends rsvp.Promise {
  then(onFulfillment, ...args) {
    return super.then(result => isolate(onFulfillment, result), ...args);
  }
}

var p = new TestPromiseFromNative(function(resolve) {
  resolve();
})
.then(null)
.catch(console.log)

var p = new TestPromiseFromRSVP(function(resolve) {
  resolve();
})
.then(null)
.catch(console.log)

function isolate(onFulfillment, result) {
  // Reset lastPromise for nested helpers
  lastPromise = null;

  let value = onFulfillment(result);

  let promise = lastPromise;
  lastPromise = null;

 return value;
}