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A JQuery data binding library for Bacon.js.

Adds stuff to Bacon.$. Is also called BJQ.


  • Binding the state of HTML input elements to Model objects that extend the Bacon.js Property API by providing a bidirectional binding
  • Composing Model objects using model.bind, Model.combine and model.lens
  • Attaching additional input EventStream to any Model by using model.addSource
  • AJAX helpers. Wrap a JQuery AJAX call into an EventStream using Bacon.$.ajax("/get/stuff"). Convert an EventStream of requests into an EventStream of responses like requests.ajax().
  • FRP extensions to JQuery. Wrap JQuery events easily into an EventStream, as in $("body").clickE()

This library is intended as a replacement for Bacon.UI. It provides the same functionality, with the addition of two-way bound Models, model composition and lenses.

Example Applications

There are example applications in the examples directory, each with a describing how they are started.

Each application does essentially the same thing and the code in the example applications is essentially just this:

  // binding for "left" text field
  left = bjq.textFieldValue($("#left"))
  // binding for "right" text field
  right = bjq.textFieldValue($("#right"))
  // make a two-way binding between these two
  // values in the two fields will now stay in sync
  // Make a one-way side effect: update label text on changes, uppercase".toUpperCase").changes().assign($("#output"), "text")
  // Add an input stream for resetting the value


The bacon.jquery API consists of methods for creating a Model representing the state of a DOM element or a group of DOM elements. This API is published as Bacon.$, and the same object is returned when using AMD or CommonJS.

###Bacon.$.textFieldValue(field [, initValue])

Creates a Model for an <input type="text"> element, given as a JQuery object. You can optionally supply an initial value.

###Bacon.$.checkBoxValue(field [, initValue])

Creates a Model for a <input type="checkbox"> element, given as a JQuery object. The value is true if the checkbox is checked and false otherwise.

###Bacon.$.selectValue(field [,initValue])

Creates a Model for a <select> element, given as a JQuery object. The value of the model corresponds to the value attribute of the selected <option> element.

###Bacon.$.radioGroupValue(fields, [,initValue])

Creates a Model for a group of <input type="radio"> elements, given as a JQuery object. The value of the model corresponds to the value attribute of the selected radio input element.

###Bacon.$.checkBoxGroupValue(fields, [,initValue])

Creates a Model for a group of <input type="checkbox"> elements, given as a JQuery object. The value of the model is an array of the value attributes of the checked checkbox input elements. For instance, if you have checkboxes and 2 of these are checked, having values a and b, the value of the Model is ["a", "b"].

TODO: add HTML/JS examples

FRP extensions to JQuery Events

BJQ adds methods to JQuery, for wrapping events into an EventStream.

For example, to wrap click events on <body> into an EventStream, you can

var clicks = $("body").clickE()

Supported methods include the following:

  • keydownE
  • keyupE
  • keypressE
  • clickE
  • dblclickE
  • mousedownE
  • mouseupE
  • mouseenterE
  • mouseleaveE
  • mousemoveE
  • mouseoutE
  • mouseoverE
  • resizeE
  • scrollE
  • selectE
  • changeE
  • submitE
  • blurE
  • focusE
  • focusinE
  • focusoutE
  • loadE
  • unloadE

FRP extensions to JQuery Effects

BJQ adds methods to JQuery, for performing animations and wrapping the result Promise into an EventStream. For example

var fadeOut = $("#thing").fadeOutE("fast")

Supported methods include the following:

  • animateE
  • showE
  • hideE
  • toggleE
  • fadeInE
  • fadeOutE
  • fadeToE
  • fadeToggleE
  • slideDownE
  • slideUpE
  • slideToggleE


BJQ provides helpers for JQuery AJAX. All the methods return an EventStream of AJAX results. AJAX errors are mapped into Error events in the stream.


Performs an AJAX request on each event of your stream, collating results in the result stream.

The source stream is expected to provide the parameters for the AJAX call.

var usernameRequest = { return { type: "get", url: "/usernameavailable/" + un } })
var usernameAvailable = usernameRequest.changes().ajax()


Performs an AJAX request and returns the results in an EventStream.

var results = Bacon.$.ajax("/get/results")


var results = Bacon.$.ajax({ url: "/get/results"})

Bacon.$.ajaxGet(url, data, dataType)

Bacon.$.ajaxGetJSON(url, data)

Bacon.$.ajaxPost(url, data, dataType)


Model API

All the BJQ methods, such as textFieldValue return a Model object, which is a Bacon.js Property, but extends that API by the following methods.


Creates a new model, with the given (optional) initial value.


Sets a new value for the model, also pushing this value to all two-way sources.


Modifies the value of the model by applying the given function to the current value. For instance, if the current value was 1 and you applied a multiplyBy2 function, the value would be set to 2.


Adds an input source for pushing values to the model. The source may be an EventStream or a Property. The method returns an EventStream that contains all changes from other sources than this.


Adds an input source of modification functions to the model. The source may be an EventStream or a Property, and is supposed to contain functions as values. Each of these functions are applied as modifications to the value of the model (as with using the modify method). The method returns an EventStream that contains all changes from other sources than this.


Makes a two-way binding between the two models.


Creates a new lensed model based on this one. For example:

    car = bjq.Model({ brand: "Ford", engine: "V8" })
    engine = car.lens "engine"

Now the engine model will have the value "V8". Also, these two models are bound both ways meaning that changes in engine are reflected to car and vice versa.

See Lenses section below for full definition of Lenses.


Creates a composite model using a template. For example:

    // Model for the number of cylinders
    cylinders = bjq.Model(12)
    // Model for the number of doors
    doors = bjq.Model(2)
    // Composite model for the whole car
    car = bjq.Model.combine {
      price: "expensive",
      engine: { type: "gas", cylinders},

The composite model has a bidirectional binding to its components. If the cylinders model is gets a change from a UI, the car model is updated accordingly. Also, if you set the value in the car model to, say {price: "affordable", engine: { type: "electric", cylinders: 0 }, doors: 4}, the cylinders model will get a new value 0.

Binding API

BJQ uses a simple Binding API for creating Model objects bound to DOM elements.


Creates a new bound Model. The options argument is an object containing the following fields:

get : zero-arg function that returns the current value from the UI

set : 1-arg function that pushes the given new value to the UI

events : an EventStream of input events from the UI. The content of these events are ignored; they are only used to trigger the polling of the new value from the UI using the get function.

initValue (optional) : initial value to be set for the model


TODO: reference to functional lenses

A lens can be defined in two ways:


Creates a lens with a p path string, such as "engine" or "engine.cylinders"

Bacon.Lens({get, set})

Creates a lens with a {get, set} pair such as { get: function(context) { .. }, set: function(context, value) { .. }}

TODO: more

Use with AMD / RequireJS

The requirejs example-app uses RequireJS, like this:

  paths: {
    "bacon.jquery": "../dist/bacon.jquery",
    "bacon": "components/bacon/dist/Bacon",
    "jquery": "components/jquery/jquery"
require(["bacon.jquery", "jquery"], function(bjq, $) {
  left = bjq.textFieldValue($("#left"))
  right = bjq.textFieldValue($("#right"))
  right.assign($("#output"), "text")

The prebuilt javascript file can be found in the dist directory, or here.

The API can be accessed using Bacon.$ or like in the above example.

Use without AMD

The plain example-app uses RequireJS, like this:

So feel free to use plain old <script> tags to include Bacon, JQuery and BJQ.

The BJQ methods are exposed through Bacon.$, so you can call them as in Bacon.$.textFieldValue(..).

The prebuilt javascript file can be found in the dist directory, or here.

There's a plain example-app that uses script tags only.

Use with Node / Browserify

BJQ is registered in the NPM repository as bacon.jquery and works fine with node-browserify.

See the browserify example-app for an example.

Use with Bower

Registered to the Bower registry as bacon.jquery. See the Example Applications, for instance requirejs example-app.


The bacon.jquery module is built using NPM and Grunt.

To build, use npm install.

Built javascript files are under the dist directory.

Automatic tests

Use the npm test to run all tests.

Tests include mocha tests under the test directory, and mocha browser tests under the browsertest directory. The test script uses mocha-phantomjs to run the browser tests headless.

The browser tests can also be run by opening the browsertest/runner.html in the browser.

The tests are also run automatically on Travis CI. See build status below.

Build Status

What next?

See Issues.

If this seems like a good idea, please tell me so! If you'd like to contribute, please do! Pull Requests, Issues etc appreciated. Star this project to let me know that you care.