判断当前tab页是否处于活动状态focus

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]) {   
        console.log('页面非激活');
    }else{
        console.log('页面激活')
    }
}
document.addEventListener(visibilityChangeEvent, onVisibilityChange);