Warden.js

Formula

Formulas are the simplets way to describe dependency of one streams from others. Conjunctive operation in time could be simply implemented via streams formulas.

Usage:

We have an markup:

<input type='text' id='a' value="0"> + <input  type='text' id='b' value="0"> + <input type='text' id='c' value="0"> ) * <input type='text' id='d' value="0"> = <input type='text' id='result'>
      

This markup represents simple algebraic expression (a + b + c ) * d = X, but all values changes over the time. We don't want to append to each input handler and observe changes of value and count final result. So we use Warden.Formula

// returns stream of given type from element #id
function from(id, type){
  return $("#" + id).stream(type);
}

//return stream which contain integer type value from stream of given source
function value(src){
  return from(src, 'keyup').map('@val()').map(parseInt);
}

//values of inputs
var a = value('a'), 
    b = value('b'),
    c = value('c'),
    d = value('d');

We prepared all streams, so let combine them with formula

var res = Warden.Formula([a,b,c,d], function(a,b,c,d){
  // in this function a,b,c,d is a simple values of adequate streams 
  return (a + b + c) * d;
});

// now res is a stream which updates with given formula
// so we can bind res's value to the input with ID equals 'result'
res.bindTo($("#result"), 'val');   

var color = value("color"),
    shape = value("shape"),
    size = value("size");

var figure = Warden.Formula([color,size,shape], function(color,size,shape){
  return "Figure now is " + size + (shape.length ? " " : " and ") + color  + " " + shape;
});

figure.bindTo($("#res"), 'html');