用query通过类来选择元素，但是index索引值却不对，我希望的是按照顺序012345这样，可是sub-nav的li索引又是从0开始
html代码

<ul class="nav nav-pills nav-stacked main-nav" role="tablist">

            <li class="nav-bar">LAYOUT</li>
            <li class="nav-bar">SIGNAL</li>
            <li class="nav-bar">USER</li>
            <li id="sys">SYSTEM SETTING
                <ul class="sub-nav">
                    <li class="nav-bar">SYSTEM TIME</li>
                    <li class="nav-bar">NET SETTING</li>
                    <li class="nav-bar">VERISION INFO</li>
                    <li data-toggle="modal" data-target="#quit">QUIT</li>
                </ul>
            </li>
        </ul>

js代码
$(".nav-bar").click(function(){

    var index=$(this).index();
    console.log(index);
});