rafa/docs/Stream-group.md

Rafa.js is a Javascript framework for building concurrent applications.

Group stream values into  categories keyed by a string; fan-out. A 
handler function can be provided that translates values to strings, otherwise
the message's value will be converted to a string and used as a key.

<aside>
```js
// group(...categories: String[, handler: Message => Message]): Stream
var stream = Rafa.stream();
var groups = { small: [], big: [] };

var grouped = stream1.group("small", "big", v => {
  var group = "big";
  if (v < 3) group = "small";
  return group;
});

grouped.small.each(v => groups.small.push(v));
grouped.big.each(v => groups.big.push(v));

stream.enumerate(Rafa.Enumerator.array([1,2,3,4]);

// groups:
//   small: [1,2]
//   big: [3,4]
```
</aside>