lib/index.esm.js
function then(onFulfilled, onRejected) {
      var reaction = newPromiseCapability(_speciesConstructor(this, $Promise));
      reaction.ok = typeof onFulfilled == 'function' ? onFulfilled : true;
      reaction.fail = typeof onRejected == 'function' && onRejected;
      reaction.domain = isNode$1 ? process$2.domain : undefined;
      this._c.push(reaction);
      if (this._a) this._a.push(reaction);
      if (this._s) notify(this, false);
      return reaction.promise;
    }
function then(onFulfilled, onRejected) {
      var reaction = newPromiseCapability(_speciesConstructor(this, $Promise));
      reaction.ok = typeof onFulfilled == 'function' ? onFulfilled : true;
      reaction.fail = typeof onRejected == 'function' && onRejected;
      reaction.domain = isNode$1 ? process$2.domain : undefined;
      this._c.push(reaction);
      if (this._a) this._a.push(reaction);
      if (this._s) notify(this, false);
      return reaction.promise;
    }
25.4.5.3 Promise.prototype.then(onFulfilled, onRejected)