js实现标签下划线平移

一.使用js实现导航行栏，点击时，下划线会跟着鼠标的点击移动。

html代码如下：

<header>
	   <div id="nav1">
	    <div id="id1" class="item">1</div>
	    <div id="id2" class="item">2</div>
	    <div id="id3" class="item">3</div>	   
	    </div>
	    <div id="line"></div>
  </header>

css代码如下：

             *{
                 margin:0;
                 padding:0;
              }
              body{
		background: url("./img/wallhaven1.png");
		  }
            .item{
            	width: 100px;
            	height: 30px;
                margin-bottom: 5px;
                margin-left: 5px;
                padding: 5px 10px;
            	background: #B89C9B;
            	text-align: center;
                line-height: 30px;
            	color:white;
            	border-radius: 10px;

            }      
           
           
            #line{
                color:red;
                width: 4px;
                height: 40px;
                background: red;
                position: absolute;
                top:0px;
                padding-right: 1px;
            }

js代码如下：

<script>
function avtiveLineTop(n) {
  document.getElementById('line').style.top = n + 'px';
};   
   var nav1 = document.getElementById("nav1");   
   var items = document.getElementsByClassName('item');  
   	   nav1.addEventListener("click",handle,false);   	  
    	 function handle(event){
    	 	 var event=event||window.event;
	       	 var target=event.target||event.srcElement;;
	       	 switch(target.id){
	       	 	case "id1": 	 	                       
                     avtiveLineTop(0);   
	       	         break;
	       	    case "id2":	       	       
	       	         avtiveLineTop(45);
	       	         break;
	       	     case "id3":
	       	         avtiveLineTop(90);
	       	         break;        	 	   
	       	 }
	       }
	</script>

效果图：

默认时，红色横线在1标签处，点击2时，红色标签，会根据移动函数进行移动，如图（2）

二.在此基础上，根据css3来实现横线的过度平滑效果。

html代码如下：

<section>
	   <ul id="nav2">
		    <li  class="item1"><a href="#" id="id11">课程学习</a></li>
		    <li  class="item1"><a href="#" id="id21">课程笔记</a></li>
		    <li  class="item1"><a href="#" id="id31">课程练习</a></li>
		    <li  class="item1"><a href="#" id="id41">课程相关</a></li>
		    <li  class="item1"><a href="#" id="id51">课程拓展</a></li>
	    </ul>
	    <div id="line1"></div>
   </section> 
   <div ></div>
  <div id="pic">
  	   <img src="./img/wallhaven3.png" alt="人物"> 
  </div>

css代码如下：

        .item1{  
                width: 100px;
            	height: 30px;
                margin-bottom: 5px;
                margin-left: 5px;
                padding: 5px 10px;          	
            	background: #1E293B;             
            	float:left;
            	text-decoration:none; 
                color:white;
                 line-height: 30px;
            	border-radius: 10px;

            }             
            
             #line1{
                color:red;
                width: 120px;
                height: 2px;
                background: red;
                position: absolute;
                top:175px;
                left:5px;
                padding-top: 1px;
               
            }
            #nav2{
            	 list-style-type: none; 
            }
            #nav2 a{
            	display: block;
                text-decoration:none; 
                color:white;
            }
            #nav2 a:hover{
            	background-color: #1E291a;
            	color:red;
            }
            #pic{
            	margin-top:80px; 
            	margin-left: 10px;
            

            }
            img{
            	width: 200px;
            	height:200px;
            	border-radius: 15px;
            }
            .effect0{
            	transform: translateX(1px);
            	transition:all  2s;
            }
            .effect{             	
            	transform: translateX(125px);
            	transition:all  2s;
            }
             .effect2{             	
            	transform: translateX(250px);
            	transition:all  2s;
            }
             .effect3{             	
            	transform: translateX(375px);
            	transition:all  2s;
            }
             .effect4{             	
            	transform: translateX(500px);            	
            	transition:all  2s;
            }
           .piceffect{
                transform: translateX(600px) scale(1.5);
                transition: all 2s;
           }

js代码如下：

var nav2 = document.getElementById('nav2'); 
var pic = document.getElementById('pic');
nav2.addEventListener("click",move,false);
function move(event){
    	 	 var event=event||window.event;
	       	 var target=event.target||event.srcElement;;
	       	 switch(target.id){
	       	 	case "id11":           
                     line1.className = "effect0";
	       	         pic.className = "effect0";
	       	         break;
	       	    case "id21":       
	       	         line1.className = "effect";
	       	         pic.className = "effect";
	       	          break;
	       	    case "id31":
	       	         line1.className = "effect2";
	       	         pic.className = "effect2";
	       	         break;
	       	    case "id41":       	    
		       	      line1.className = "effect3";
		       	      pic.className = "effect3";
		       	      break;
	       	    case "id51":	       	      
	       	        line1.className = "effect4";
	       	        pic.className = "effect4";
	       	        break;	       	 	   
	       	 }
	       	    }    
	  pic.addEventListener("click",showbig,false);
	  function showbig(){	  	
	  	pic.className="piceffect";
	  }

效果图：

当鼠标没有点击标签时，横线默认是在第一个标签下，如图：

当点击任何一个标签，下划线和图片就会平滑的过度到点击的那个标签下，如图：