jquery给轮播图的第一张设置class样式

<div id="myCarousel" class="carousel slide">
    <ol class="carousel-indicators">
        <li data-target="#myCarousel" data-slide-to="0" class="active"></li>
        <li data-target="#myCarousel" data-slide-to="1"></li>
        <li data-target="#myCarousel" data-slide-to="2"></li>
        <li data-target="#myCarousel" data-slide-to="3"></li>
    </ol>
    <div class="carousel-inner">
        <div class="item active">
            <img src="./images/lunbo1.jpg">
        </div>
        <div class="item">
            <img src="./images/lunbo2.jpg">
        </div>
        <div class="item">
            <img src="./images/lunbo3.jpg">
        </div>
        <div class="item">
            <img src="./images/lunbo4.jpg">
        </div>
    </div>
</div>

<!-- js引入 -->
<script src="js/jquery-3.1.1.min.js"></script>
<script src="js/bootstrap.min.js"></script>
<script>
    $(function () {
        $('#myCarousel').carousel({interval: 4000});
        //获取轮播的第一个，然后添加class样式
        $(".carousel-inner").find("div").first().attr("class","item active");
        $(".carousel-indicators").find("li").first().attr("class","active");
    });
</script>