rafa/docs/Stream-listener.md

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

Return a function that handles a variable number of arguments, converts
those arguments to a single value, and then writes that value to a 
channel, which is enumerated by this stream.
The returned function is meant to be used as an event handler.

<aside>

```js
// listener(kind: String, Channel): ((...args) => _)
var button = document.querySelector("button[value='2']")
var stream = Rafa.stream();
var result = 0;

stream.each(mouseEvent => result = mouseEvent.target.value);
button.addEventListener("click", stream.listener());
button.click();

// result: 2
```
</aside>


The listener can also generate different types of messages to the stream, 
i.e. value, error, and done messages, by setting the kind parameter to either
"Value", "Error", or "Done".

<aside>

```js
var button = document.querySelector("button[value='oops']")
var stream = Rafa.stream();
var result = 0;

stream.error(mouseEvent => result = mouseEvent.target.value);
button.addEventListener("click", stream.listener("Error"));
button.click();

// result: oops
```
</aside>


If a channel is not provided, the listener method will create one automatically
and configure it with a buffer size of 0 (see Channels). You can also configure
the channel it will create by passing in the size and action parameters that
a Channel constructor expects.

<aside>

```js
var button = document.querySelector("button[value='2']")
var stream = Rafa.stream();
var result = 0;

stream.each(mouseEvent => result += mouseEvent.target.value);
button.addEventListener("click", stream.listener("Value", 1, "rotate"));
button.click();
button.click();

// result: 4
```
</aside>