They are not part of the specification nor is there a standard way of accessing them that you could use to get the internal state of the promise to construct a polyfill. However, you can convert any standard promise into one that has these values by creating a wrapper,

function MakeQueryablePromise(promise) {

    // Don't create a wrapper for promises that can already be queried.

    if (promise.isResolved) return promise;

    

    var isResolved = false;

    var isRejected = false;



    // Observe the promise, saving the fulfillment in a closure scope.

    var result = promise.then(

       function(v) { isResolved = true; return v; }, 

       function(e) { isRejected = true; throw e; });

    result.isFulfilled = function() { return isResolved || isRejected; };

    result.isResolved = function() { return isResolved; }

    result.isRejected = function() { return isRejected; }

    return result;

}

This doesn't affect all promises, as modifying the prototype would, but it does allow you to convert a promise into a promise that exposes it state.