js获取网站根目录

<script type="text/javascript">
    function getRootPath() {
        var strFullPath = window.document.location.href;
        var strPath = window.document.location.pathname;
        var pos = strFullPath.indexOf(strPath);
        var prePath = strFullPath.substring(0, pos);
        var postPath = strPath.substring(0, strPath.substr(1).indexOf('/') + 1);
        return (prePath + postPath+"/");
    }
    alert(getRootPath());
</script>