js implements mouse in and out card switching content

<div class="sports-purple">
   <div class="all">
    
    <!-- Contents -->
    <div class="content">
     
     <div class="first-block">
      <!-- Sidebar for content -->
      <div class="aside">
       <h2>Categories</h2>
       <ul class="lis">
        <li class="sna">
         <a href="#">Sneakers</a>
         <div id="sub">
           <div><a href="#">Running Shoes</a></div>
           <div><a href="#">Basketball Shoes</a></div>
           <div><a href="#">Soccer Shoes</a></div>
           <div><a href="#">Hiking Shoes</a></div>
           <div><a href="#">Skateboarding Shoes</a></div>
           <div><a href="#">Dance shoes</a></div>
           <div><a href="#">Tennis Shoes</a></div>
           <div><a href="#">Cycling Shoes</a></div>
           <div><a href="#">Walking Shoes</a></div>
           <div><a href="#">Golf Shoes</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Sports Clothing</a>
         <div id="sup">
           <div><a href="#">Jackets</a></div>
           <div><a href="#">Base Layers</a></div>
           <div><a href="#">Shirts</a></div>
           <div><a href="#">Sets/Suits</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Cycling</a>
         <div id="cyc">
           <div><a href="#">Bicycle</a></div>
           <div><a href="#">Bicycle Parts</a></div>
           <div><a href="#">Bicycle Accessories</a></div>
           <div><a href="#">Bicycle Repair Tools</a></div>
           <div><a href="#">Cycling Clothings</a></div>
           <div><a href="#">Cycling Shoes</a></div>
           <div><a href="#">Electric Bicycle</a></div>
           <div><a href="#">Electric Bicycle Part</a></div>
           <div><a href="#">Self Balance Scooters</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Finshing</a>
         <div id="fin">
           <div><a href="#">Fishing Rods</a></div>
           <div><a href="#">Fishing Reels</a></div>
           <div><a href="#">Rod Combo</a></div>
           <div><a href="#">Fishing Lures</a></div>
           <div><a href="#">Fishing Lines</a></div>
           <div><a href="#">Fishhooks</a></div>
           <div><a href="#">Fishing Tackle Boxes</a></div>
           <div><a href="#">Fishing Float</a></div>
           <div><a href="#">Fishing Net</a></div>
           <div><a href="#">Fishing Rope</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Hunting</a>
         <div id="hun">
           <div><a href="#">Bow & Arrow</a></div>
           <div><a href="#">Hunting Optics</a></div>
           <div><a href="#">Hunting Cameras</a></div>
           <div><a href="#">Weapon Lights</a></div>
           <div><a href="#">Hunting Bags & Holsters</a></div>
           <div><a href="#">Hunting Knife</a></div>
           <div><a href="#">Hunting Lights</a></div>
           <div><a href="#">Hunting Decoy</a></div>
           <div><a href="#">Hunting Gun Accessories</a></div>
           <div><a href="#">Scope Mounts & Accessories</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Camping & Hiking</a>
         <div id="cam">
           <div><a href="#">Tents</a></div>
           <div><a href="#">Sun Shelter</a></div>
           <div><a href="#">Sleeping Bags</a></div>
           <div><a href="#">Climbing Bags</a></div>
           <div><a href="#">Outdoor Stoves</a></div>
           <div><a href="#">Outdoor Tablewares</a></div>
           <div><a href="#">Picnic Bags</a></div>
           <div><a href="#">Water Bags</a></div>
           <div><a href="#">Camping Mat</a></div>
           <div><a href="#">Outdoor Lighting</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Fitness & Body Building</a>
         <div id="fit">
           <div><a href="#">Fitness Equipments</a></div>
           <div><a href="#">Outdoor Fitness Equipment</a></div>
           <div><a href="#">Boxing</a></div>
           <div><a href="#">Yoga</a></div>
           <div><a href="#">Gymnastics</a></div>
           <div><a href="#">Martial Arts</a></div>
           <div><a href="#">Weight Lifting</a></div>
           <div><a href="#">Weight Lifting Gloves</a></div>
           <div><a href="#">Fitness Gloves</a></div>
           <div><a href="#">Dance shoes</a></div>
         </div>
        </li>
        <li class="sna">
         <a href="#">Musical Instruments</a>
         <div id="mus">
           <div><a href="#">Guitar</a></div>
           <div><a href="#">Guitar Parts & Accessories</a></div>
           <div><a href="#">Violin</a></div>
           <div><a href="#">Violin Parts & Accessories</a></div>
           <div><a href="#">Woodwind Instruments</a></div>
           <div><a href="#">Percussion Instruments</a></div>
           <div><a href="#">Instrument Bags & Cases</a></div>
           <div><a href="#">Brass Instruments</a></div>
           <div><a href="#">Keyboard Instruments</a></div>
         </div>
        </li>
       </ul>
       
       <div class="flip">
        <a href="#"class="page pagedown">
         <img src="../images/arrow.png">
        </a>
        <a href="#"class="page pageup">
         <img src="../images/arrow.png">
        </a>
        <div class="tail">
         1/3
        </div>
       </div>
      </div>
      
     </div>
 
 
    </div>
 
   </div>
 
  </div>
 
</div>

*{
 margin:0;
 padding:0;
}
a{
 text-decoration: none;
}
li{
 list-style: none;
}
 
.sports-purple{
 width: 100%;
 background-color: #EEEEEE;
 position: relative;
 padding-top: 10px;
}
 
/* Start of content sidebar style */
.first-block{
 width: 100%;
 height: 500px;
}
.aside{
 width: 280px;
 height: 465px;
 background-color: #FFFFFF;
 margin-left: 150px;
}
.aside h2{
 color: #a059cb;
 text-align: left;
 line-height: 60px;
 border-bottom: 1px solid #A059CB;
 font-weight: 400;
 font-size: 18px;
 padding: 0 20px;
}
.lis li{
 border-bottom: 1px solid #EEEEEE;
 line-height: 40px;
 height: 40px;
 margin: 0 20px 0 20px;
}
.lis li a{
 color: #000000;
 font-size: 13px;
}
.list a:hover,.lis li a:hover{
 color: #FF4500;
 text-decoration: underline;
}
 
.flip{
 margin: 20px 0 20px 0px;
 line-height: 30px;
}
.flip .pagedown{
 width: 30px;
 height: 30px;
 border-radius: 4px;
 display: inline-block;
 border: 1px solid #a5a5a5;
 position: relative;
 left: 20px;
 overflow: hidden;
 margin-bottom: 20px;
}
.flip .pagedown img{
 position: absolute;
 left: 10px;
 top: 13px;
}
.flip .pageup{
 width: 30px;
 height: 30px;
 border-radius: 4px;
 display: inline-block;
 border: 1px solid #a5a5a5;
 position: relative;
 left: 40px;
 overflow: hidden;
 margin-bottom: 20px;
}
.flip .pageup img{
 position: absolute;
 left: -30px;
 top: -32px;
}
.flip .tail{
 float: right;
 margin-right: 130px;
 font-size: 12px;
}
 
#sub, #sup, #cyc,
#fin, #hun, #cam, #fit, #mus
 width: 300px;
 height: 403px;
 position: absolute;
 left: 400px;
 top: 70px;
 font-size: 13px;
 border: 1px solid #A059CB;
 background-color: #FFFFFF;
 z-index: 10;
 display: none;
}
.aside li:hover{
 border-left: 4px solid #A059CB;
 border-top: 1px solid #A059CB;
 border-bottom: 1px solid #A059CB;
 padding-left: 10px;
 margin-left: 20px;
 background-color: #FFFFFF;
}
 
#sub div,#sup div,
#cyc div,#fin div,
#hun div,#cam div,#fit div,
#mus div{
 margin-left: 20px;
}

// Get li according to class name
var lis = document.getElementsByClassName("sna");
 
//Loop through the li tags with class name sna for(var i = 0;i<lis.length;i++){
 //Register mouse move event for li lis[i].onmouseover = function(){
  /* this: li with class name sna */
  //console.log(this);
  /* this.children: Get the child elements under the li tag*/
  // console.log(this.children);
  var next = this.children;
  //next[1]: Among the two sub-elements under li, the subscript of the label of the element to be displayed is 1
  next[1].style.display = "block";
 };
 //Register mouse out event for li lis[i].onmouseout = function(){
  var next = this.children;
  next[1].style.display = "none";
 };
}