subscribing hash change

hashchange.js

    if ("onhashchange" in window) {
         window.onhashchange = function () {
              alert(window.location.hash);
         }
    }
    else {
        var prevHash = window.location.hash;
        window.setInterval(function () {
           if (window.location.hash != prevHash) {
              prevHash = window.location.hash;
              alert(window.location.hash);
           }
        }, 100);
    }