二级导航栏

二级导航栏可以说是非常好做了(●'◡'●)

html

<div class="whole">
  <ul>
    <li class="li">1
      <ul class="list">
        <li>1</li>
        <li>2</li>
        <li>3</li>
      </ul>
    </li>
    <li class="li">2
      <ul class="list">
        <li>1</li>
        <li>2</li>
        <li>3</li>
      </ul>
    </li>
    <li class="li">3
      <ul class="list">
        <li>1</li>
        <li>2</li>
        <li>3</li>
      </ul>
    </li>
  </ul>
</div>

三个大标签，每个大标签包含三个小标签

css

*{
        margin: 0;
        padding: 0;
        list-style: none;
      }
      .whole{
        margin: 0 auto;
        margin-top: 100px;
      }
      .whole>ul>li{
        float: left;
      }
      li{
        text-align: center;
        width: 150px;
        height: 50px;
        line-height: 50px;
        background: cornflowerblue;
        transition: all 0.5s ease;
        cursor: pointer;
        box-sizing: border-box;
        border-bottom: 2px solid transparent;
      }
      .list>li{
        height: 0;
        visibility: hidden;
        transition: all 0.3s ease;
        overflow: hidden;
        position: relative;
      }
      .li:hover .list>li{
        height: 50px;
        visibility: visible;
      }

通过改变高度实现下拉效果，用transition属性使得动画更自然

javascript

for(let i=0;i<$('.li').length;i++){
  (function(i){
    $('.li:eq('+i+')').mouseover(function(){
      $('.li:eq('+i+')').css("background","#777777").css("border-bottom","2px solid blue");
      for(let j=0;j<$('.li').length;j++){
        (function(j){
          $('.li:eq('+i+') li:eq('+j+')').mouseover(function(){
            $('.li:eq('+i+') li:eq('+j+')').css("background","#777777");
          }).mouseout(function(){
            $('.li:eq('+i+') li:eq('+j+')').css("background","cornflowerblue");
          });
        })(j);
      }
    }).mouseout(function(){
      $('.li:eq('+i+')').css("background","cornflowerblue").css("border-bottom","2px solid transparent");
    });
  })(i);
}

用循环遍历所有li，使得鼠标移到标签上时改变属性

这样就完成二级导航栏了