Promise chaining example

gistfile1.txt

// proof of concept for promise chaining
function chain(obj) {
  let stack = [];

  let proxy = new Proxy(obj, {
    get: (target, name, receiver) => {
      if (name == 'finally' || name == "done") {
        return function(callback) {
          return replayStack(obj, stack, callback);
        }
      }
      else {
        return function() { stack.push([name, arguments]); return proxy; }
      }
    }
  });

  return proxy;
}

let replayStack = function(obj, stack, done) {
  let then = function(promise, obj, next) {
    return promise.then(function(result) {
      if (typeof result != 'object') {
        result = obj; // keep the chain
      }

      return result[next[0]].apply(result, next[1]);
    });
  }

  let promise = new Promise((resolve, reject) => {
    resolve(obj);
  });

  for (let next of stack) {
    promise = then(promise, obj, next);
  }

  return promise.then(done);
}