# observable

A function as representation of a trackable mutable value.

[Interactive Demo](http://dominictarr.github.com/observable)

It's basically just a `function` that can be called in 3 ways,
If an observable is called with no arguments `f()`, it returns the current value.
If it is called with an argument `f(value)`, it set that as the value.

``` js
var o = require('observable')
var v = o()

//set the value
v(Math.random())

//get the value
v()
```

And, finally, if an observable is called with another function, 
`f(function (v) {...})`, it _calls_ that function with the new value, 
whenever the value changes.

## value

``` js
var o = require('observable')
var v = o()

v(0)

setInterval(function () {
  v(v() + 1)
}, 500)

v
```

How is this demo updating in real-time like that?
It's because `observable` is integrated into 
[hyperscript](https://github.com/dominictarr/hyperscript)!

## input, & transform

observe a input field, and transform it into different string.
this transformation is a one way observable.

``` js
var o = require('observable')
var h = require('hyperscript')
var yourName
  
h('div', 
  h('h3', 'hello, what is your name?',
    yourName = h('input', {placeholder: 'enter name'})
  ),
  h('h2', o.transform(o.input(yourName), function (v) {
    return v ? 'Happy Birthday ' + v.toUpperCase() + ' !!!': ''
  }), {style: {'font-family': 'Comic Sans MS'}})
)
```

Oh, wow! wasn't that easy! and we did a lot of things there!

* made hyper text that updated in realtime
* read from an input as you typed
* transformed user input

And there is many other cool things we can do to!

# not

Invert a boolean `observable`

``` js
var o = require('observable')
var h = require('hyperscript')
var _i, i
h('div',
  _i = h('input', {type: 'checkbox'}),
  'checked:', i = o.input(_i, 'checked', 'change'),
  ' !checked:', o.not(i)
)
```

Hmm, I wonder if we could couple two things interms of each other?

``` js
var o = require('observable')
var h = require('hyperscript')
var _i = h('input', {type: 'checkbox'})
var _j = h('input', {type: 'checkbox'})
var i = o.input(_i, 'checked', 'change')
var j = o.input(_j, 'checked', 'change')

//just make i != j & j != i
i(Math.random() < 0.5)

o.bind2(o.not(i), j)

h('div', _i, _j)
```

## compute

Compute a value from others, like a computed value in SQL.

``` js
var o = require('observable')
var h = require('hyperscript')
var i, j
h('div', 
  i = h('input', {placeholder: 'first name'}),
  j = h('input', {placeholder: 'last name'}),
  h('h1', 'Greetings, ',
    o.compute([o.input(i), o.input(j)], function (f, l) {
      return f + ' ' + l + (f && l ? ' !' : '')
    })
  )
)
```

## hover & focus

``` js
var h = require('hyperscript')
var o = require('observable')

h('div', 
  strong = h('strong', {
      contentEditable: true,
      style:{display: 'inline-block'}
    }, 
    "editable thing"
  ),
  h('ul', 
    h('li', 'focus: ', o.focus(strong)), 
    h('li', 'hover: ', o.hover(strong))
  )
)
```

## screen/scroll

``` js
var o = require('observable')
var h = require('hyperscript')

window.addEventListener('resize')

```

## License

MIT