Riot.js: minimal observable example

HTML

<div id="test"></div>

<script type="riot/tag">
  <test>
    <p>{ message }</p>
    
    this.message = 'some message';
  </test>
</script>

<script>
/* Riot WIP, @license MIT, (c) 2015 Muut Inc. + contributors */

;(function(window) {
  // 'use strict' does not allow us to override the events properties https://github.com/muut/riotjs/blob/dev/lib/tag/update.js#L7-L10
  // it leads to the following error on firefox "setting a property that has only a getter"
  //'use strict'

  var riot = { version: 'WIP', settings: {} },
      ieVersion = checkIE()

riot.observable = function(el) {

  el = el || {}

  var callbacks = {},
      _id = 0

  el.on = function(events, fn) {
    if (typeof fn == 'function') {
      fn._id = typeof fn._id == 'undefined' ? _id++ : fn._id

      events.replace(/\S+/g, function(name, pos) {
        (callbacks[name] = callbacks[name] || []).push(fn)
        fn.typed = pos > 0
      })
    }
    return el
  }

  el.off = function(events, fn) {
    if (events == '*') callbacks = {}
    else {
      events.replace(/\S+/g, function(name) {
        if (fn) {
          var arr = callbacks[name]
          for (var i = 0, cb; (cb = arr && arr[i]); ++i) {
            if (cb._id == fn._id) { arr.splice(i, 1); i-- }
          }
        } else {
          callbacks[name] = []
        }
      })
    }
    return el
  }

  // only single event supported
  el.one = function(name, fn) {
    function on() {
      el.off(name, on)
      fn.apply(el, arguments)
    }
    return el.on(name, on)
  }

  el.trigger = function(name) {
    var args = [].slice.call(arguments, 1),
        fns = callbacks[name] || []

    for (var i = 0, fn; (fn = fns[i]); ++i) {
      if (!fn.busy) {
        fn.busy = 1
        fn.apply(el, fn.typed ? [name].concat(args) : args)
        if (fns[i] !== fn) { i-- }
        fn.busy = 0
      }
    }

    if (callbacks.all && name != 'all') {
      el.trigger.apply(el, ['all', name].concat(args))
    }

    return el
  }

  return...

JavaScript

riot.mount('#test','test');