Eyebrow

Minimalistic JavaScript application architecture

Eyebrow or just Brow is a minimal library for front-end JavaScript application development inspired by React and Redux. It is a simple View library/architecture which bundles together simple templating, view and event management, routing and data/state store in a very minimalistic way.

Apart from the library itself, Eyebrow provides a set of common and good practices which are based on traditional HTML and JavaScript concepts such as event binding on the DOM.

Installation

To install Eyebrow you can do it either download the eyebrow.js file from this repo, from a CDN or install it via NPM:

npm install eyebrow

or

<script src="//npmcdn.com/eyebrow" type="text/javascript"></script>

You can then import Eyebrow to your page using webpack, Browserify or a <script> tag.

Principles

Application orientation

In Eyebrow you can instantiate an application by calling the Eyebrow function:

var App = Eyebrow();       // like this
var App2 = new Eyebrow();  // or like this

View functions

Every view, event or action in an Eyebrow application is a function of the type

f : State × (Data...) → State

where Data... is a variadic list of arguments which contains data fed to the view/event/action.

When thought of as an action in response to a route, the Data argument contains the route parameters, for example: in a blogging application, the route http://yourblog.com/#/some-author/post-name could be associated with a function of type:

viewPostFromAuthor : State × Author × Post → State

Views in an Eyebrow application are then just functions which are called in response to a route change (see Routing section).

Functions

Being App and Eyebrow application:

App(action[, data])

The core of the library are the applications, the functions returned by the Eyebrow() function. It can be seen as an event emitter. When calling this function - which we'll call App = Eyebrow() from now on -, there can be four different cases in following precedence order:

1. View refresh – When called with no parameters, App() refreshes the current view, the view function(s) assigned to the current route are called once again with the same parameters;
2. View action – When called with one or both parameters, App(actionName, data...) tries to call the method actionName on the current view with data... parameters, if it exposes such method;
3. Application action – When no view method for actionName is found, App(actionName, data...) emits an event of name actionName, which, when registered by the application with App.on(actionName, callback), calls such event callback;
4. Route action – Last but not least, when none of the above cases is met before, when no method for actionName is found, then actionName is treated as a route route. The window hash is set to route and the views whose registered RegExp match route are called.

Views

In Eyebrow - as stated before -, views are just functions of the type State × (Data...) → State, that is, any function which, given a State and a set of input data, calculates a new application State.

Eyebrow view functions must be pure, they shall not produce any side effects. Given the same State and Data input, it should calculate the same output State, because only when the State returned by the view function is different from the last state, the view gets refreshed.

Templating

Templating in Eyebrow is left to the user himself to decide what's better to use. Templates are just functions registered under a name on the Eyebrow application with the function:

App.template : String × Function → [(String, Function)]

In the examples, mainly Handlebars templates are used, but you can also set it up to use custom functions, e.g.:

App.template('my_template', (items) => {
  return items.map((item) => `<li class="${item.active ? 'active' : ''}">${item.name}</li>`);
});

In order to render a template, the App.render function must be used, e.g.:

App.render('my_template', 'div#main', exampleItems);

Routing

Routing in Eyebrow is done by watching the location.hash property. When of the onhashchange event, the registered routes are matched against the new hash.

Routes can be registered with the function

App.route : RegExp × Function → [(RegExp, Function)]

which registers a regular expression as a route. The whole location.hash (without the # character) is matched against the given RegExp. And the given view function must be of type State × (Data...) → State.