function storageAvailable(type) {
    try {
        var storage = window[type],
            x = '__storage_test__';
        storage.setItem(x, x);
        storage.removeItem(x);
        return true;
    }
    catch(e) {
        return false;
    }
}

window.localStorageSupported = false;
if (storageAvailable('localStorage')) {
    window.localStorageSupported = true;
}
else
{
    window.localStorageSupported = false;
}

(function(){

  if ("performance" in window == false) {
      window.performance = {};
  }

  Date.now = (Date.now || function () {  // thanks IE8
    return new Date().getTime();
  });

  if ("now" in window.performance == false){

    var nowOffset = Date.now();

    if (performance.timing && performance.timing.navigationStart){
      nowOffset = performance.timing.navigationStart
    }

    window.performance.now = function now(){
      return Date.now() - nowOffset;
    }
  }

})();

window.vis = (function(){
    var stateKey,
        eventKey,
        keys = {
                hidden: "visibilitychange",
                webkitHidden: "webkitvisibilitychange",
                mozHidden: "mozvisibilitychange",
                msHidden: "msvisibilitychange"
    };
    for (stateKey in keys) {
        if (stateKey in document) {
            eventKey = keys[stateKey];
            break;
        }
    }
    return function(c) {
        if (c) document.addEventListener(eventKey, c);
        return !document[stateKey];
    }
})();

function getHiddenProp(){
    var prefixes = ['webkit','moz','ms','o'];

    // if 'hidden' is natively supported just return it
    if ('hidden' in document) return 'hidden';

    // otherwise loop over all the known prefixes until we find one
    for (var i = 0; i < prefixes.length; i++){
        if ((prefixes[i] + 'Hidden') in document)
            return prefixes[i] + 'Hidden';
    }

    // otherwise it's not supported
    return null;
}
function isHidden() {
    var prop = getHiddenProp();
    if (!prop) return false;

    return document[prop];
}