JavaScript如何识别当前页面是否处于激活状态？

//检测当前窗口是否隐藏状态

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';

    }



    return null;

}