states is an object that carries the arbitrary data (or what you can think of as "settings") of a single component. Since behavior functions listen to changes in states, you can use states to drive animations. States cannot be shared between components, and only a component's event functions can modify state values, via the $state.set operation (see below).


State values are stored as properties in the component's states object:

FamousFramework.component('example', {
    states: {
        clickCount: 0

Behaviors functions respond to changes in these defined states. When a state value (e.g. clickCount) is listed as a parameter to a behavior function, that function will be called whenever that value changes.

FamousFramework.component('example', {
    behaviors: {
        '#someNode': {
            'rotation-z': function(clickCount){
                return clickCount;

For example, the rotation-z behavior function will be called when clickCount state value changes. To actually go about changing clickCount, we use the $state object in conjunction with an event function.

The $state API

Event functions are able to dependency-inject a special $state object that gives access to special getter/setter methods for accessing and mutating the state values enclosed by the component.

FamousFramework.component('example', {
    events: {
        '#foo': {
            'click': function($state) {
                // manipulate state here

Let's look quickly at the APIs that this state manager instance exposes to you. For brevity, we'll omit the rest of the boilerplate in the examples below.


The most basic methods are .get() and .set(), which work best when dealing with simple values and operations:

// states are { foo: 1 }
$state.get('foo'); // Returns `1`
$state.set('foo', 2); // Sets the state `foo` to `2`


If we want to transition a state value to another value smoothly over time, we can pass a transition options object as the third argument:

// states are { foo: 0 }
$state.set('foo', 3, { duration: 1000 });

The above will transition the state value foo from 0 to 3 smoothly over the course of one second. We can also supply an easing curve:

$state.set('foo', 3, { duration: 1000, curve: 'easeOutBounce' });

See the easing curves table for a full list of curves.

Chaining transitions

If you want to transition a state value after some state value has completed a transition, use the .thenSet() method:

$state.set('foo', 1, { duration: 1000 })
      .thenSet('bar', 2, { duration: 5000 })
      .thenSet('baz', 3.14);

Complex / nested state values (arrays and objects)

States can store any JSON-serializable value including arrays and objects. Arrays are especially helpful when dealing with $repeat control flow behaviors.

If you wish to access a single value within a states array, the .get() method accepts the state name and the index you wish to access passed to it in an array:

 // states are: { stateArray: ['blue','red','green'] }
 $state.get(['stateArray', 1])  // returns 'red'

Similar to the .get() method, you can set a single value in a states array by passing the .set() method an array with the name and target index as its first parameter and the new value as the second:

// states are: { stateArray: ['blue','red','green'] }
$state.set(['stateArray', 2], 'purple')
// after, states are: { stateArray: ['blue','red','purple']} 

For objects, the API is very similar, except instead of using the element index integer, you use a string for the name of the property key:

// states are: { stateObj: { foo: 'bar' } }
$state.set(['stateObj', 'foo'], 'ABC');
// after, states are: { stateObj: { foo: 'ABC' } }