test.js

var storage = (function() {
  if (window.localStorage) {
    //alert('localStorage supported');
  } else if (Cookies){
    //alert("Local storage is not supported, using Cookies");
  } else {
    alert('exception');
  }

  var key = 'event';
  return {
    setLocalData: function(msg) {
      var oldVal = '';
      if (window.localStorage) {
        oldVal = localStorage.getItem(key) || '';
        localStorage.setItem(key,  oldVal + msg);
      } else if (Cookies) {
        oldVal = Cookies.get(key) || '';
        Cookies.set(key, oldVal + msg, { expires: Infinity });
      }
    },
    getLocalData: function() {
      if (window.localStorage) {
        return localStorage.getItem(key) || '';
      } else if (Cookies) {
        return Cookies.get(key) || '';
      }
    },
    removeLocalData: function() {
      if (window.localStorage) {
        localStorage.removeItem(key);
      } else if (Cookies) {
        Cookies.expire(key);
      }
    }
  }
})();

// #1 beforeunload
window.onbeforeunload = function () {
  storage.setLocalData("\n #1 onbeforeunload " + document.title + ' on ' + (new Date()).toString());
};

// # 2 pagehide
window.onpagehide = function () {
  storage.setLocalData("\n #2 onpagehide " + document.title + ' on ' + (new Date()).toString());
};

// # 3 unload
window.onunload = function () {
  storage.setLocalData("\n #3 onunload " + document.title + ' on ' + (new Date()).toString());
};

window.onload = function() {
  storage.setLocalData("\nonload " + document.title + ' on ' + (new Date()).toString());

  setInterval(showLog, 1000);

  id('clearbtn').onclick = function() {
    storage.removeLocalData();
    showLog();
  }
};

function id(str) {
  return document.getElementById(str);
}

function showLog() {
  id('log').value = storage.getLocalData() || '[empty]';
}