WINJS.BINDING.AS
▪ var target = document.getElementById('target'),
a = { x : 1 },
b = WinJS.Binding.as(a);
b.bind('x', function(newVal, oldVal) { target.innerHTML = newVal; });
console.log(target.innerHTML); // 1
b.x = 2;
console.log(target.innerHTML); // 2
b.x = 3;
console.log(target.innerHTML); // 3