32.js 判断当前页面是否被浏览

可以通过document.hidden属性判断当前页面是否是激活状态。 
兼容性：IE10+，Firefox10+,Chrome14+,Opera12.1+,Safari7.1+ 
兼容性写法示例：

    var hiddenProperty = 'hidden' in document ? 'hidden' :
        'webkitHidden' in document ? 'webkitHidden' :
        'mozHidden' in document ? 'mozHidden' :
        null;
    var visibilityChangeEvent = hiddenProperty.replace(/hidden/i, 'visibilitychange');
    var onVisibilityChange = function(){
        if (!document[hiddenProperty]) {
            document.title='被发现啦(*´∇｀*)';
        }else{
            document.title='藏好啦(つд⊂)  ';
        }
    }
    document.addEventListener(visibilityChangeEvent, onVisibilityChange);