gistfile1.ts

class Promise<X> {
  map<B>(onValue: (x: X) => B): Promise<B> {
    AS.assertParameter(onValue, "onValue");
    return new Promise<B>((resolve, reject) => {
      this.parsePromise.then(x => {
        resolve(onValue(x));
      }, e => {
        reject(e);
        return Parse.Promise.as();
      });
    });
  }

  then<B>(onValue: (x: X) => Promise<B>, onError?: (err: any) => Promise<B>): Promise<B> {
    AS.assertParameter(onValue, "onValue");
    return new Promise<B>((resolve, reject) => {
      this.parsePromise.then(x => {
        resolveCallback(x, onValue, resolve, reject);
      }, e => {
        resolveCallback(e, onError, resolve, reject);
        return Parse.Promise.as();
      });
    });
  }
}

function resolveCallback<X,B>(
  value: X,
  callback: (x: X) => any,
  resolve: (x?: B) => void,
  reject: (e: any) => void
): void {
  var val = callback(value);
  AS.assert("Expected " + val + " to be promise", () => Promise.is(val));
  val.parsePromise.then((y: B) => {
    resolve(y);
  }, (err: any) => {
    reject(err);
    return Parse.Promise.as();
  });
}