reactive

Simple and Flexible template and view binding engine with support for custom bindings and real-time updates on model changes.

Installation

With component:

$ component install component/reactive

With npm via browserify:

$ npm install reactive

Quickstart

Rendering a basic html template with a predefined data model.

var view = reactive('<p>Hello {name}!</p>', {
  name: 'Adam'
});

// you can add the view "element" to the html whenever you want
// view.el contains the html element
document.body.appendChild(view.el);

<p>Hello Adam!</p>

Handling events

Reactive provides an easy way to register handlers for dom events via predefined “bindings”.

var handlers = {
  clickme: function(ev) {
    // console.log('button clicked');
  }
};

var template = '<button on-click="clickme">clickme</button>';
var view = reactive(template, {}, {
  delegate: handlers
});

A recommended approach is to wrap the reactive instance inside of your own View classes. See the Views example.

Iteration

Iteration is achieved by using the each binding on the element you wish to iterate.

var template = '<ul><li each="people">{this}</li></ul>';
var model = {
  people: ['Sally', 'Billy']
};

var view = reactive(template, model);

<ul>
  <li>Sally</li>
  <li>Billy</li>
</ul>

You can push (pop, shift, etc) to the array and the view will be updated accordingly.

model.people.push('Eve');

<ul>
  <li>Sally</li>
  <li>Billy</li>
  <li>Eve</li>
</ul>

Hiding and showing elements

DOM elements can be shown or hidden via the data-visible and data-hidden bindings.

Using the following html template.

var tmpl = '<p data-hidden="items.length">no items</p>' +
  '<ul data-visible="items.length"><li each="items">{this}</li></ul>';
var model = { items: [] };
var view = reactive(tmpl, model);

When rendering the above, we will see no items, because the array is empty.

model.items.push('one');

Will change the output to · one and hide no items. Notice how data-visible and data-hidden act in opposite directions.

API

reactive(string | element, model, [options])

Create a new reactive instance using string or element as the template and model as the data object. This binds a DOM element to a model.

If you do not have a data model and want to specify options, you can pass null or {}. Remember you must have this argument before the options argument.

Options

option	type	description
delegate	object, instance	an object or instance defining overrides and handlers for properties and events
adapter	function	defines how reactive will interact with the model to listen for changes
bindings	object	define custom bindings (see bindings docs below)

Bind object to the given element with optional view object. When a view object is present it will be checked first for overrides, which otherwise delegate to the model object.

set(prop, val)

Set the property prop to the given value val in the view.

set({prop: val})

Set multiple properties prop and given values val in the view.

get(prop)

Get the value for property prop.

bind(name, fn)

Recommend using bindings option during construction instead. Will be removed in the future.

Create a new binding called name defined by fn. See the writing bindings section for details.

use(fn)

Use a reactive plugin. fn is invoked immediately and passed the reactive instance.

destroy()

Destroy the reactive instance. This will remove all event listeners on the instance as well as remove the element from the dom.

Fires a destroyed event upon completion.

Model Adapters

Model Adapters provide the interface for reactive to interact with your model implementation. By using a custom adapter you can support models from backbone.js, modella, bamboo, etc…

You can make reactive compatible with your favorite model layer by creating a custom adapter. Changes to your model will cause the reactive view to update dynamically. The following API is required for all adapters.

constructor

The adapter option is a function which accepts one argument, the model and should return an instance with all of the adapter methods implemented. The constructor will be called as a function - without the new keyword.

As an example, the builtin adapter’s constructor is:

function Adapter(model) {
  if (!(this instanceof Adapter)) {
    return new Adapter(model);
  }

  var self = this;
  self.model = model;
};

In addition to the constructor, the adapter must implement these methods:

• subscribe
• unsubscribe
• unsubscribeAll
• set
• get

subscribe(prop, fn)

Subscribe to changes for the given property. When the property changes, fn should be called.

Adapter.prototype.subscribe = function(prop, fn) { ... };

unsubscribe(prop, fn)

Unsubscribe from changes for the given property. The fn should no longer be called on property changes for prop.

unsubscribeAll

Unsubscribe all property change events. Used when a reactive instance is being torn down.

set(prop, val)

Set the property prop to the given value val.

get(prop)

Get the value for property prop

Stock Adapters

• reactive-bamboo - an adapter for bamboo.
• reactive-backbone - an adapter for Backbone models.

Plugins

Custom bindings to extend reactive are listed on the plugins wiki page

Interpolation

Bindings may be applied via interoplation on attributes or text. For example here
is a simple use of this feature to react to changes of an article’s .name property:

<article>
  <h2>{name}</h2>
</article>

Text interpolation may appear anywhere within the copy, and may contain complex JavaScript expressions
for defaulting values or other operations.

<article>
  <h2>{ name || 'Untitled' }</h2>
  <p>Summary: { body.slice(0, 10) }</p>
</article>

Reactive is smart enough to pick out multiple properties that may be used, and
react to any of their changes:

<p>Welcome { first + ' ' + last }.</p>

Interpolation works for attributes as well, reacting to changes as you’d expect:

<li class="file-{id}">
  <h3>{filename}</h3>
  <p><a href="/files/{id}/download">Download {filename}</a></p>
<li>

Declarative Bindings

By default reactive supplies bindings for setting properties, listening to events, toggling visibility, appending and replacing elements. Most of these start with “data-*” however this is not required.

data-text

The data-text binding sets the text content of an element.

data-html

The data-html binding sets the inner html of an element.

data-<attr>

The data-<attr> bindings allows you to set an attribute:

<a data-href="download_url">Download</a>

each

The each binding allows you to iterate a collection of objects within the model:

<ul>
  <li each="children">{name}</li>
</ul>

The model is expected to have a children property whose value is an array.

on-<event>

The on-<event> bindings allow you to listen on an event:

<li data-text="title"><a on-click="remove">x</a></li>

remove is expected to be a method on the specified delegate object:

var delegate = {
  remove: function(ev) {
    console.log('Removing thing!');
    ...
  }
}

reactive(template, model, {
  delegate: delegate
});

data-append

The data-append binding allows you to append an existing element:

<div class="photo" data-append="histogram"></div>

The histogram property on the model is expected to contain a DOM element.

data-replace

The data-replace binding allows you to replace an existing element, and carryover its attributes:

<div class="photo" data-replace="histogram"></div>

The histogram property on the model is expected to contain a DOM element.

data-{visible,hidden}

The data-visible and data-hidden bindings conditionally add “visible” or “hidden” classnames so that you may style an element as hidden or visible.

<p data-visible="hasDescription" data-text="truncatedDescription"></p>

data-visible will add a visible class if the property is truthy. For arrays, use the .length property to trigger on empty or non-empty arrays.

data-hidden is the opposite of visible and will add a visibile class if the value is false and .hidden class if the value is truthy.

data-checked

Toggles checkbox state:

<input type="checkbox" data-checked="agreed_to_terms">

data-selected

Toggles option state:

<option data-selected="selected"></option>

Writing bindings

To author bindings, simply create a function that will accept two arguments, the element and binding value. For example, here is a binding which removes an element when truthy:

function removeIf(el, property){
  var binding = this;
  binding.change(function() {
    if (binding.value(property)) {
      el.parentNode.removeChild(el);
    }
  });
};

var template = '<span remove-if="name">no name</span>';
var view = reactive(template, { name: 'foobar' }, {
 bindings: {
  'remove-if': removeIf
 }
});

Notice that you can call the binding whatever you want when you create your view allowing you to select appropriate names. Binding authors should recommend names that make sense.

Here is another binding which uses momentjs to pretty print a javascript date.

var template = '<span moment="timestamp" format="MMM Do YY"></span>';
var view = reactive(template, { timestamp: new Date() }, {
 bindings: {
  'moment': momentFormat
 }
});

function momentFormat(el, property) {
  var binding = this;
  var format = el.getAttribute('format');
  binding.change(function () {
     var val = binding.value(property);
     el.innerText = moment(val).format(format);
  });
};

Would output the following html

<span>Mar 3rd 14</span>

You can easily re-use such bindings by making them plugins and enabling them on your instance with .use()

Interpolation

Some bindings such as data-text and data-<attr> support interpolation. These properties are automatically added to the subscription, and react to changes:

<a data-href="/download/{id}" data-text="Download {filename}"></a>

Notes

Get creative! There’s a lot of application-specific logic that can be converted to declarative Reactive bindings. For example here’s a naive “auto-submit” form binding:

<div class="login">
  <form action="/user" method="post" autosubmit>
    <input type="text" name="name" placeholder="Username" />
    <input type="password" name="pass" placeholder="Password" />
    <input type="submit" value="Login" />
  </form>
</div>

var reactive = require('reactive');

var view = reactive(document.querySelector('.login'), {}, {
 bindings: {
  autosubmit: autosubmit
 }
});

function autosubmit(el){
  el.onsubmit = function(e){
    e.preventDefault();
    var path = el.getAttribute('action');
    var method = el.getAttribute('method').toUpperCase();
    console.log('submit to %s %s', method, path);
  }
};

View patterns

Typically a view object wraps a model to provide additional functionality, this may look something like the following:

function UserView(user) {
  this.user = user;
  this.view = reactive(tmpl, user, {
    delegate: this
  });
}

UserView.prototype.clickme = function(ev){ ... }

Often a higher-level API is built on top of this pattern to keep things DRY but this is left to your application / other libraries.

For more examples view the ./examples directory.

Run examples and tests

$ git clone https://github.com/component/reactive.git
$ cd reactive
$ npm i
$ make
$ open examples

$ make test

License

MIT