A Javascript Library for Building Apps

b8rjs.com | bindinator.com | github | npm | [cdn] (https://www.jsdelivr.com/package/npm/@tonioloewald/b8r?path=dist) | b8r-native

Note b8r is now published to npm as b8rjs. I'll update the cdn link when I've confirmed it has updated.

Bindinator (b8r) is a fairly small (24kB compressed) "front-end" javascript library with no transitive dependencies that implements the model-view-controller (MVC) design pattern along with state-management ("reactive programming") and separation of concerns.

|| Model || View || Controller | objects (and maybe code) | HTML + CSS | code | {text: 'hello world'} | <input data-bind="value=model.text"> | { clear(){ b8r.reg.model.text = ''} }

It's bind because b8r lets you use HTML data-attributes to bind data from the model and event-handlers from the controller code with the views.

And it's inator because once you register an object, bindings are managed automatically and efficiently.

So, in this simple example, if the user edits the text in the <input> field, then model.text will be updated as will the text in the <p>, and if you update the registry, e.g. b8r.reg.model.text = "foo", then the <input> field and <p> will be updated, which is also how the clear() function in the controller works.

You can use the console to see how b8r.reg.model is updated and how modifying it automatically updates the view. You can also modify the controller to do something else.

You might also want to turn on Chrome's "paint flashing" tools and see how efficiently b8r updates the DOM.

Oh, and don't worry, the documentation site intentionally exposes b8r as a global otherwise you wouldn't be able to do this. Normally b8r is hidden in a closure in production.

b8r's Principle of Laziness

• write less code
• that runs as written
• is easier to read
• easier to debug
• quicker to test
• has fewer bugs (bugs > k × loc)
• that loads faster
• uses less memory, and thus…
• runs faster

This is 360° laziness. Everyone does less work to get smaller, faster, cheaper results.

Wait what? It's not that you can pick all three from "good, fast, cheap", it's that you're operating within a better framework (philosophy, not code library) that lets you spend more time on what's important to your app.

Laziness drives every design decision in b8r.

And b8r is lazy too.

• It doesn't do things for the browser that the browser knows how to do (like parse HTML).
• Nor implement a new templating language.
• Nor require special debugging tools.
• Or add zillions of runtime dependencies. Actually, it doesn't add any.

Basic Principles

Put data into b8r's registry to bind it to a path

b8r.reg.foo = {bar: 17, baz: {lurman: 'hello world'}}

Bind "data-paths" to the DOM with data-bind

<input data-bind="value=foo.baz.lurman">

…and stuff "just works"

Now, changes in the DOM update the bound data. And changes made to the data (via the registry) update the DOM, e.g.

b8r.reg.foo.baz.lurman = 'goodbye world'

Binding arrays is just as simple:

<ul>
  <li data-list="foo.list:id" data-bind="text=.name"></li>
</ul>

And then bind a list:

b8r.reg.foo.list = [{id: 1, name: 'Tomasina'}, {id: 2, name: 'Deirdre'}, {id: 3, name: 'Harry'}]

(Or do it the other way around)

Here's all of the above in a live "fiddle". Try adding this above the <script> tag (and then clicking Refresh):

<div data-bind="text=foo.baz.lurman"></div>

Now try editing the text in the text field. You could also try replacing the binding in the <input> with data-bind="value=foo.list[id=3].name". Try editing that!

Or try entering this in the debugger console:

b8r.reg.foo.list['id=3'].name = 'Harriet'

Digging a little deeper

There's no magic!

A web application comprises DOM elements styled with CSS (views), and wired up to behaviors implemented in Javascript (or, moving forward, Webassembly), and using data obtained from services.

With b8r, you bind paths to DOM elements using the data-bind attribute, and you bind javascript objects to paths using b8r.reg..., and b8r does the rest.

When you assign objects to b8r.reg you are binding data to paths, e.g.

b8r.reg.foo = {bar: 'hello'}

Now, the object {bar: 'hello'} is bound to the path foo, so foo.bar points to 'hello', b8r.reg.foo.bar and b8r.get('foo.bar') will both yield 'hello'.

When you assign new values to the registry, you are in fact altering values inside an object bound to the "root" of the path. b8r.reg.foo.path.to.whatever = ... changes values inside the object bound to foo. Using the reg to set values also tells b8r that the values have been changed, allowing it to perform updates.

You must register an object to a name before you can change values inside it. But you can always bind to a path.

In this example text is the target, example.name is the data-path. The root name (example) is bound to the path via b8r.register.

Note the use of a handlebars-like interpolated string (it doesn't do eval, it just looks up paths). Usually bindings won't contain {{...}} and are treated as bare data-paths. You can try to change the binding to data-bind="text=example.name" or data-bind="text={{example.name}} says “hi”".

Note that ES6 template-string-like ${…} syntax is also supported, but deprecated (it causes lint issues).

You can update data directly using b8r.reg, e.g.

b8r.reg.example.name = 'Trump'

Try it in the console!

Interacting with b8r in the console

Unlike typical "fiddles" b8r's inline examples are not isolated in their own <iframe>s—it's all happily running in the same body. By default, b8r doesn't leave anything at all in global namespace.

In the b8r documentation app I've exposed b8r to let you play around. This is generally useful for debugging.

If b8r weren't exposed you could enter something like the line below in the browser console:

import('./path/to/b8r.js').then(({default}) => {window.b8r = default});

One day you might find this trick useful in a pinch!

Note that you need to point the import() at the same exact version of b8r you're using elsewhere — otherwise you won't be able to see the registry.

Bind arrays to the DOM with data-list

Binding arrays is just as simple, using the data-list attribute:

Within a list binding, paths beginning with a period are relative to the list instance. (Look at the <li> tags in the preceding example.)

A few of things to try in the console:

b8r.reg.example2.list['id=ncc-1031]'].name = 'Veejer'
b8r.reg.example2.list.push({id: 17, name: 'Clear Air Turbulence'})
b8r.reg.example2.fleet = 'Culture + Federation'
b8t.reg.example2.list.splice(1,1)

Finally note that a path comprising just a period binds to the entire list item, so if you bind to a list of bare strings then data-bind="text=." will get the string,

Bindings work both ways

Most updates are handled automatically:

Bind events to methods with data-event

Events are bound via data-paths just as data. In this example click is the event type and example4.click is the path to the event.

Try this in the console (and then click the button again):

b8r.reg.example4.click = () => alert('I changed the event handler')

Any of these snippets can be converted into reusable components by saving them as (say) example.component.html. (Each of these snippets is in fact a complete component.)

You can load a component using b8r.component('path/to/example'). Once loaded, it will automatically be inserted where-ever you use <b8r-component name="example">. Components can be nested exactly as you would expect.

Supports Web-Components

b8r provides convenience methods for creating Web Components, a.k.a. Custom Elements, and its bindings play nice with them (e.g. waiting for a custom-element's definition before attempting to bind values to it).

Oh yeah, b8r components are themselves instances of the <b8r-component> web-component.

Create Components with HTML or JavaScript

Each of these little inline examples is a component written in HTML. (b8r expects components written in html to be in files named some-name.component.html.) HTML components aren't as nice as pure Javascript components.

A simple HTML component:

<style>
  ._component_ {
    background: yellow
  }
</style>
<h1 data-bind="text=_component_.caption"></h1>
<button data-event="click:_component_.alert">
  Click Me!
</button>
<script>
  /* global set, get */
  if(!get().caption) {
    set({caption: 'I is component'})
  }
  set({
    alert(){
      window.alert(get().caption)
    }
  })
</script>

The equivalent as Javascript:

export default {
  css: `
    _component_ {
      background: yellow;
    }
  `,
  html: `
    <h1 data-bind="text=_component_.caption"></h1>
    <button data-event="click:_component_.alert">
      Click Me!
    </button>
  `,
  load({get, set}) {
    if(!get().caption) {
      set({caption: 'I is component'})
    }
    set({
      alert(){
        window.alert(get().caption)
      }
    })
  }
}

But Javascript components are more flexible and can, for example, set properties before the component is inserted into the DOM via initialValue(). We don't need to check if caption has been set because we're earlier in the component life-cycle.

export default {
  css: `
    _component_ {
      background: yellow;
    }
  `,
  html: `
    <h1 data-bind="text=_component_.caption"></h1>
    <button data-event="click:_component_.alert">
      Click Me!
    </button>
  `,
  initialValue({get}) => ({
    caption: 'I is component',
    alert(){
      window.alert(get().caption)
    }
  })
}

When you want to get into the details of building components, there are sections on components and on b8r's component API.

Add components with <b8r-component>

A stateful component looks like this:

And to use the preceding component, you'd write something like this:

<b8r-component path="path/to/clock"></b8r-component>

You can build a To Do List app like this:

Note: the to-do list component in the preceding example is bound to a global path, as is the one below. So the two share data automatically. This is not an accident. If you want a component to have its own unique data, you can bind to _component_.

Composing Components [data-children]

You can create composable components by using data-children inside a component. Within a component, the element with the data-children attribute (if any) will receive the children of the element bound to the component.

E.g. in the snippet below:

<b8r-component name="parent">
  <b8r-component name="child"></b8r-component>
</b8r-component>

If the parent component has an element with the data-children attribute, when it loads, the child will be moved into it. In the example below, the tab-selector component creates one tab for each child.

Dog Food!

bindinator.com is built using b8r (along with numerous third-party libraries, none of which are global dependencies). The inline fiddle component used to display interactive examples is 343 lines including comments, styles, markup, and code. b8r isolates component internals so cleanly from the rest of the page that the fiddle doesn't need to use an iframe.

b8r with npm in five minutes

Here's a really quick start to working with b8r to build a web app. (If you're interested in building a desktop app, you can try b8r-native.)

mkdir path/to/project
cd path/to/project
npm init

Accept all the defaults. (We'll ignore the entry point for now.)

npm install @tonioloewald/b8r—save

You'll need something to serve pages, a simple option is:

npm install http-server—save-dev

Now create a simple web page:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>hello world</title>
</head>
<body>
  <h1 data-bind="text=app.message"></h1>
  <input data-bind="value=app.message">
  <button data-event="click:app.speak">Speak</button>
  <b8r-component path="node_modules/@tonioloewald/b8r/components/photo-tabs"></b8r-component>
  <script type="module">
    // you can also use ../b8r/dist/b8r.min.mjs (minified)
    // or ../b8r/source/b8r.js (source code)
    import b8r from './node_modules/@tonioloewald/b8r/dist/b8r.mjs'

    window.b8r = b8r // so we can play with it in console

    b8r.reg.app = {
      message: 'hello world',
      speak() {
        alert(b8r.reg.app.message)
      }
    }
  </script>
</body>
</html>

…and save it as index.html.

Now run:

npx http-server .

And open http://localhost:8080 in your browser.

Go into your dev tools console (Cmd+Shift+J in Chrome, Cmd+Option+C in Safari, Cmd+Option+I in Firefox) and try:

b8r.reg.app.message                     // should print "hello world"
b8r.reg.app.message = 'laziness rules!' // updates the value in the input
b8r.reg.app.speak()                     // same as clicking the button

In a Nut

• bind paths to DOM elements using data-bind.
• bind paths to objects using b8r.reg.name (or b8r.reg['your name']) = { … }.
• access and modify values bound to paths using b8r.reg.path.to.value.
• bind arrays to the DOM using data-list.
• bind events to event handlers using data-event.
• bind components to the DOM using <b8r-component>.
• use web-components without worrying about binding.

We can register data (models and controllers) and load components (views) asynchronously. If the user clicks the button before the controller is registered, the controller method will be called when it becomes available.

Copyright ©2016-2022 Tonio Loewald