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Hierarchical router library for single page applications.


Browser support

SauceLabs Status

With IE8/IE9, The router won't throw any errors at script evaluation time, so it can be used to support these browsers in degraded mode.


What is Abyssa?

Abyssa is a stateful, hierarchical client side router.
What does stateful mean? it means all states are not equal and abyssa knows how to go from one state to another efficiently.
Abyssa does only one thing: Routing.
Upon entering a state, it can be rendered using any technique: Direct DOM manipulation, client or server side templating, with the help of a binding library, etc. A state can even be abstract and not render anything.

Abyssa is versatile

Abyssa can be used like a traditional stateless url -> callback router:

  article: State('articles/:id', articleEnter),
  articleEdit: State('articles/:id/edit', articleEditEnter)

Or we can leverage abyssa's state machine nature:

  article: State('articles/:id', {
    enter: loadArticle,

    show: State('', articleEnter),
    edit: State('edit', articleEditEnter)

Now we can freely switch between viewing and editing an article without any pause because the article data is loaded in the parent state and can be shared in the child states.

Abyssa is performant

What is the main advantage of stateful routers? Performance: Less redraws, less wasteful data loading, less wasteful setUp logic, etc.
When going from a state A to a state B, as far as a stateless router is concerned, everything has to be done from scratch even if the two states are closely related. Trying to optimize state transitions by hand is going to be awkward and lead to an explosion of custom state variables. On the other hand, abyssa make it simple to reason about what makes each state different and thus compute the minimum set of changes needed to transition from state A to state B.


Here, Abyssa will simply swap the red bit for the green bit. Why should everything be redrawn? It's slower and the software would lose all the state implicitly stored in the previous DOM.

Read this excellent blog post for more information: Make the most of your routes


Using abyssa as a commonJS/browserify module

npm install abyssa
var Router = require('abyssa').Router;

Using abyssa as a global or as an AMD module
Use one of the provided prebuilt files in the target folder.


Error handling

Since transitions are asynchronous and backed by promises, errors are caught centrally.
By default, any error occuring during the transition will simply be rethrown. This behavior might be unsuitable in production and can be disabled with the following code:

  router.transition.failed.add(function(newState, oldState, error, preventDefault) {
    preventDefault(); // Do not let the router rethrow the error
    // do something with the passed Error instance.



A few notes:

  • Only leaf-states can be transitionned to.
  • Each transition step can return a promise to temporarily halt the transition. The resolved promise value will be passed as the second argument of the next step's callback.
  • There can be several root states. The router doesn't enforce the use of a single, top level state like some state machine implementations do.

The transition from the state A1 to the state B would consist of the following steps:

A1 exit -> (Resolve A1 exit promise if applicable) -> PA exit -> (Resolve PA exit promise if applicable) -> B enter



configure (options: Object): Router

Configure the router before its initialization. The available options are:

  • enableLogs: Whether (debug and error) console logs should be enabled. Defaults to false.
  • interceptAnchors: Whether anchor mousedown/clicks should be intercepted and trigger a state change. Defaults to true.
  • notFound: The State to enter when no state matching the current path query or name could be found. Either a State instance or a string representing the fullName of an existing state can be passed. Defaults to null.
  • urlSync: How the router state and the URL should be kept in sync. Defaults to true. Possible values are:
    • true: The router uses the history pushState API.
    • false: The url is never read or updated. The starting state is the path-less, default state.
    • 'hash': The router uses the hash part of the URL for all browsers.
  • hashPrefix: Customize the hash separator. Set to '!' in order to have a hashbang like '/#!/'. Defaults to empty string.

init (initState: String, initParams: Object): Router

Initialize the router.
The router will immediately initiate a transition to, in order of priority:
1) The init state passed as an argument (useful for testing and debugging)
2) The state captured by the current URL

addState (name: String, state: State): Router

Add a new root state to the router.
Returns the router to allow chaining.

state (stateName: String, params: Object, flashData: Any): Promise[StateWithParams]

state (pathQuery: String, flashData: Any): Promise[StateWithParams]

Request a programmatic state change.
Only leaf states can be transitionned to.
While you can change state programmatically, the more idiomatic way to do it is sometimes using anchor tags with the proper href.

Two notations are supported:

// Fully qualified state name
state('', {id: 33, filter: 'desc'})  
// Path and (optionally) query

The flashData argument can be used to expose custom data for the next transition. This data will no longer be available after that transition.

state('', {}, 123);
// Then, in any state participating in the transition: this.router.flash === 123

redirect (stateName: String, params: Object, flashData: Any): Promise[StateWithParams]

redirect (pathQuery: String, flashData: Any): Promise[StateWithParams]

An alias of state. You can use redirect when it makes more sense semantically.

backTo (stateName: String, defaultParams: Object, flashData: Any): Promise[StateWithParams]

Attempt to navigate to 'stateName' with its previous params or
fallback to the defaultParams parameter if the state was never entered.

reload(): Promise[StateWithParams]

Reload the current state with its current params.
All states up to the root are exited then reentered.
This can be useful when some internal state not captured in the url changed and the current state should update because of it.

link (stateName: String, params: Object): String

Compute a link that can be used in anchors' href attributes
from a state name and a list of params, a.k.a reverse routing.

previousState(): StateWithParams

Returns the previous state of the router or null if the router is still in its initial state.

currentState(): StateWithParams

Returns the current state of the router.

isFirstTransition(): Boolean

Returns whether the router is executing its first transition.

path(): String

Returns the path portion of the current url

query(): String

Returns the query portion of the current url

params(): Object

Returns all params (path and query) associated to the current state

queryParams(): Object

Returns the query params associated to the current state

paramsDiff(): Object

Returns the diff between the current params and the previous ones

var diff = router.paramsDiff();

  update: {
    id: true
  enter: {
    q: true
  exit: {
    section: true
  all: {
    id: true,
    q: true,
    section: true


The router dispatches some signals. The signals' API is: add, addOnce and remove.
Unless specified otherwise, all signal handlers receive the current state and the old state as arguments (of type StateWithParams).


Dispatched when a transition started.


Dispatched when a transition either completed, failed or got cancelled.
The exact signal type is passed as a third argument: 'completed', 'failed' or 'cancelled'.


Dispatched when a transition successfuly completed.


Dispatched when a transition failed to complete.


Dispatched when a transition got cancelled.


Dispatched when a transition was prevented by the router.
The router prevents the transition when the next state and params are identical to the current ones.
Handlers will only receive one argument: The current state.


Shorter alias for transition.completed: The most commonly used signal.

Usage example

Declarative construction

// Create a router with one state named 'index'.
var router = Router({
  index: State()

Programmatic construction

var router = Router();
router.addState('index', State());


StateWithParams is the merge between a State object (created and added to the router) and params (both path and query params, extracted from the URL when transitions occur).
Instances of StateWithParams are returned from router.previousState(), router.currentState() and passed in signal handlers.

state: State

The state reference

params: Object

The path and query params set for this state

isIn(fullName: String):Boolean

Returns whether this state or any of its parents has the given fullName.


var router = Router({

  books: State('books', {
    data: { myData: 33 },

    listing: State(':kind')


var state = router.currentState();

// state looks as follow:

  state: State(),
  params: {kind: 'scifi', limit: 10},
  isIn // state.isIn('books') == true



States represent path segments of an url.
A state can own a list of query params: While all states will be able to read these params, isolated changes to these will only trigger a transition up to the state owning them (it will be exited and re-entered). The same applies to dynamic query params.
How much you decompose your applications into states is completely up to you;
For instance you could have just one state:


Or four different states to represent that path:

State('some', {
  child: State('path', {
    grandchild: State(':slug', {
      grandgrandchild: State(':id')

Rest segments

Additionaly, the last path segment can end with a * to match any number of extra path segments:


// All these state changes will result in that state being entered:  

// router.state('path'); // === undefined
// router.state('path/other'); // === 'other'
// router.state('path/other/yetAnother'); // === 'other/yetAnother'

addState (name: String, state: State): State

Add a child state.
Returns the current state to allow chaining.

data (key: String, value: Any): Any | State

Get or Set some data by key on this state.
child states have access to their parents' data.
This can be useful when using external models/services as a mean to communicate between states is not desired.
Returns the state to allow chaining.

router: Router

A back reference to the router.
This property is available after router init (e.g inside an state.enter()).

name: String

The name of this state.
This property is available after router init (e.g inside an state.enter()).

fullName: String

The fully qualified name of this state.
This property is available after router init (e.g inside an state.enter()).

parent: State

The parent of this state, or null if this state is a root.
This property is available after router init (e.g inside an state.enter()).

parents: Array[State]

The list of parent states, starting with the nearest ones.
This property is available after router init (e.g inside an state.enter()).

root: State

The root state in this state tree.
This property is available after router init (e.g inside an state.enter()).

children: Array[State]

The children of this state.
This property is available after router init (e.g inside an state.enter()).

async (promiseOrValue: Object): Promise

Shortcut for Async.
This property is available after router init (e.g inside an state.enter()).

Declarative properties

When creating a State instance with an option object, the following properties have a special meaning and are reserved for abyssa:
data, enter, exit, update
All other properties should be child states.

enter (params: Object, value: Any): void

Specify a function that should be called when the state is entered.
The params are the dynamic params (path and query alike in one object) of the current url.
This is where you could render the data into the DOM or do some general work once for many child states.

exit (params: Object, value: Any): void

Same as the enter function but called when the state is exited. This is where you could teardown any state or side effects introduced by the enter function, if needed.

update (params: Object, value: Any): void

The update callback is called when the router is moving to the same state as the current state, but with different path/query params.
Specifying an update callback can be seen as an optimization preventing doing wasteful work in exit/enter, e.g removing and adding the same DOM elements that were already present in the document before the state change.

var router = router({
  people: State('people/:id', {
    enter: function() {},
    update: function() {},
    exit: function() {},

During init, enter will be called.

Later, if the router transitions from 'people/33' to 'people/44', only update will be called. If an update callback wasn't specified, exit then enter would have been called in succession.

data: Object

Custom data properties can be specified declaratively when building the state. If more data properties are set later using, value), they will all be merged together.

Usage examples


A state represented by the path "articles", with a child state named "item" represented by the dynamic path "id".
When the router is in the state "articles.item" with the id param equal to 33, the browser url is http://yourdomain/articles/33

var router = Router({
  articles: State('articles', {
  item: State(':id', {
    // state definition

Or using the imperative form:

var router = Router();
var articles = State('articles');  

articles.addState('item', State(':id'));

Construction shorthand

It is common to only have an enter callback for a state so a short way to express it is provided:

var state = State('articles', function enter(params) {
  // Do things synchronously here

  this.async(myPromise).then(function(data) {
    // Do things asynchronously here

Pathless states

A state represented by the path "articles" with a path-less child state named "show"
When the router is in the state "", the browser url is http://yourdomain/articles

var state = State('articles': {
  show: State() // Equivalent to: show: State('', {})

router.addState('articles', state);

Query strings

Now the articles state also tells us it owns the query param named 'filter' in its state hierarchy.
This means that any isolated change to the filter query param (meaning the filter was added, removed or changed but the path remained the same) is going to make that state exit and re-enter so that it can process the new filter value. If you do not specify which state owns the query param, all states above the currently selected state are exited and reentered, which can be less efficient. Also, Enumerating the possible query strings is mandatory if you want these to appear when using reverse routing or name-based state changes.

var state = State('articles?filter': {
  show: State()

Setting state data

You can set arbitrary data declaratively by just specifying a custom property in the State options.
This data can be read by all descendant states (Using'myArbitraryData')) and from signal handlers.
For more elaborated use cases, you can store the data in a custom external service or model.

var state = State('articles?filter': {
  data: { myArbitraryData: 66 },
  show: State()

// The data can also be read inside signal handlers
router.transition.ended.add(function(oldState, newState) {
  // Do something based on'myArbitraryData')

Creating a state hierarchy declaratively

var state = State('articles', {
  enter: function(params, ajaxData) { console.log('articles entered'); },
  exit: function() { console.log('articles exit'); },

  // A child state is simply a property of type 'State'
  item: State(':id', {
    enter: function(params) { console.log('item entered with id ' +; }

Creating a state hierarchy programmatically

var state = State('articles');
state.enter = function(params, ajaxData) { console.log('articles entered'); };
state.exit = function() { console.log('articles exit'); };

var item = State(':id');
item.enter = function(params) { console.log('item entered with id ' +; };

state.addState('item', item);


Async is a convenient mean to let the router know some async operations tied to the current state are ongoing.
The router will ignore (The fulfill/reject handlers will never be called) these promises if the router state changes in the meantime.
This behavior is useful to prevent states from affecting each other (with side effects such as DOM mutation in the promise handlers)
You can have as many Async blocks as required.

Example 1:

var Async = Abyssa.Async;

var state = State('articles/:id': {

  enter: function(params) {
    var data = $.ajax('api/articles/' +;

    // Do things that should be done synchronously here, like setting up the basic layout.

    // Then load the data and act on it asynchronously.

    Async(data).then(function(article) {
      // Render article safely; the router is still in the right state.

    // Or, equivalently:

    this.async(data).then(function(article) {



Example 2:

var Async = Abyssa.Async;

var state = State('articles/:id': {

  enter: function(params) {
    $('button.refresh').click(function() {
      // The user clicked on a button: Load some data before performing the action.
      // Loading the data is asynchronous, and the response should be ignored if the user
      // navigated away to another state in the meantime.
      Async(loadData()).then(function(data) {
        // Perform the action safely; the router is still in the right state.

Anchor interception

By default, the router will intercept anchor clicks and automatically navigate to a state if some conditions are met (left button pressed, href on the same domain, etc).
This behavior can be turned off by using the corresponding router configuration setting
You may want to turn off anchor interception on mobile optimised apps and make manual router.state() calls on touch events.

You can also intercept mousedown events instead of the usual click events by using a data-attribute as follow:

<a data-nav="mousedown" href="/">

If a same-domain link should not be intercepted by Abyssa, you can use:

<a data-nav="ignore" href="/">


Abyssa uses the following libraries:

crossroads.js: A stateless, solid traditional low level router. Abyssa builds on top of it.
signals.js: A dependency of crossroads.js; Provide an alternative to string based events. Abyssa uses signals instead of events.
q.js: The reference implementation of Promise/A+. This is used internally to orchestrate asynchronous behaviors.

Code examples

Demo app

Demo: Abyssa demo async
Source: Abyssa demo async source

Abyssa + React



Highlight the selected primary navigation item

Assuming the following highlight function is in scope:

function highlight(navItem) {
  $('li.nav.' + navItem).addClass('active');

We can either:

1) Observe all state changes externally

var router = Router({

  section1: State('section1', {
    data: { navItem: 'section1' } // custom data property; seen by any substate.

  section2: State('section2', {
    data: { navItem: 'section2' }


router.changed.add(function(state) {
  // or


2) Create a specialized State factory to deal with that common concern

function NavState(path, options) {
  var enter = options.enter;

  options.enter = function(params) {
  return State(path, options);

var router = Router({

  section1: NavState('section1'),
  section2: NavState('section2')


Handling the change of some params differently in update

update is an optional hook that will be called whenever the router moves to the same state but with updated path/query params.

Not all params are equal, a change in the path param representing the resource id may induce more work than the change of some secondary query param.

Example of a conditional update:

var state = State({
  enter: function(params) {

  update: function(params) {
    var diff = state.router.paramsDiff();

    // The id was changed
    if ( {
    // Some other params were changed
    else {
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