get height without jquery

var getHeight = function(){
    var viewport = new Object();
    viewport.height = 0;
    // the more standards compliant browsers (mozilla/netscape/opera/IE7) 
    //use window.innerWidth and window.innerHeight
    if (typeof window.innerHeight != 'undefined')
    {
        viewport.height = window.innerHeight
    }
    else if (typeof document.documentElement != 'undefined'
    && typeof document.documentElement.clientHeight !=
    'undefined' && document.documentElement.clientHeight != 0)
    {
        viewport.height = document.documentElement.clientHeight
    }
    else
    {
        viewport.height = document.getElementsByTagName('body')[0].clientHeight
    }
    return viewport.height;
};

var docHeight = getHeight();