prototype_hash_change_listener.js

/*
 * hash_change_listener(hash_check_interval)
 *
 * Prototype method for launching a "hash:change" custom event when the
 * page's #anchor changes.
 *
 * Examples: adding a class to the current page anchor.
 *
 *   document.observe('hash:change', function(event) {
 *     var div = $(window.location.hash.replace(/^#/, ''))
 *     if (div) {
 *       $$('.current_anchor').invoke('removeClassName', 'current_anchor')
 *       div.addClassName('current_anchor')
 *     }
 *   })
 *
 *   hash_change_listener(300)
*/

function hash_change_listener(hash_check_interval) {
  var hash_current = null
  var fire_on_change = function() {
    if (window.location.hash != hash_current) {
      document.fire('hash:change')
      hash_current = window.location.hash
    }
  }
  fire_on_change()
  return setInterval(fire_on_change, hash_check_interval)
}