var a = valueStream($("#a"));

var b = valueStream($("#b"));

​

a.log("A:");

b.log("B:");

​

// map the streams to more sensible number values

a.map(str2Number);

b.map(str2Number);

​

// combine the streams to create sum

var sum = a.combine(b.plus);

// use onValue to show sum

sum.onValue(showSum);    

// combine the streams to create product and show

// it in the correct span

​

function valueStream(element) {

  return element

    .asEventStream("keyup")

    .map(".currentTarget.value");

}

​

function str2Number(str) {

  return Number(str);

}

​

function showSum(result) {

  $("#sum").text(result);

}