promise.js

function F(fn) {
    return function (/* arguments */) {
        var args = [this].concat(Array.prototype.slice.call(arguments));
        return new Promise(function (resolve, reject) {
            Promise.all(args).then(function (/* arguments */) {
                try {
                    Promise.resolve(
                        fn.apply(arguments[0].shift(), arguments[0])
                    ).then(resolve, reject);
                } catch (e) {
                    reject(e);
                }
            }, reject);
        });
    }
}

function C(obj) {
    function Proxy() { }

    // Synthesise a "get" method for property access
    Proxy.prototype.get = F(function (p) {
        return this[p];
    }).bind(obj);

    for (m in obj.constructor.prototype) {
        Proxy.prototype[m] = F(obj.constructor.prototype[m]).bind(obj);
    }

    return new Proxy();
}

function Number(i) {
    this.i = i;
}

Number.prototype.add = function (j) {
    return this.i + j;
}

Number.prototype.sub = function (j) {
    return this.i - j;
}

var log = console.log.bind(console);

var n = new Number(8);
var p = C(n);

p.add(3).then(log);
p.add(5).then(log);