gistfile1

    'passing': function (done) {
        var a = function (self, x, callback) {
            return callback(self, x + 10);
        };

        var B = function () {
            this.y = 10;
        };
        
        B.prototype.go = function () {
            a(this, 10, function (self, value) {
                self.y += value;
                done();
            });
        };
        
        var b = new B();
        b.go();
    },