How to use JavaScript to implement navigation bar sample code sharing-JS Tutorial-php.cn

How to use JavaScript to implement navigation bar sample code sharing

黄舟

Release： 2017-07-25 09:22:18

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Use js to implement a simple navigation bar. Steps to use js to achieve a certain effect: 1. Implement CSS layout; 2: JS implementation principle; 3. Write CSS code.

<!DOCTYPE html><html><head><meta charset="UTF-8"><title>Insert title here</title><style>
     ul {           
padding:0px;           
margin:0px;           
list-style:none;     
}

     a {           
text-decoration:none;           
background-color:#f1f1f1;           
display:block;           
width:50px;           
text-align:center;     
}

     .list {           
display:none;     
}


     ul ul{          
width:140px;          
border:solid #000 1px;  
          position:absolute;     
}

     ul ul li {         
text-align:center;     
}

     .item {       
 position:relative;    
  }
  </style>
  </head>
  <body>
     <ul>
         <li class="item" id="item">
             <a href="#" id="link">微博</a>
             <ul class="list" id="list">
                <li>私信</li>
                <li>评论</li>
                <li>@我</li>
             </ul>

         </li> 
     </ul></body><script>
      var link = document.getElementById("link");      
  var item = document.getElementById("item");      
  var list = document.getElementById("list");
      item.onmouseover = show;
      item.onmouseout = hide;      function show(){
             list.style.display = "block";   
             link.style.background = "yellow";
      }      function hide(){
          list.style.display = "none";
      }</script></html>

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JS method to remove an element from view:
(1)display:none;(does not occupy the document flow)
(2)visibility:hidden;(hide an element , still occupying the document flow)
(3) Set the transparency to 0, which is opacity:0; (In IE browser, the transparency can be set like this filter:alpha(opacity=0);)
(4) Setting Margin value, for example, set the margin value to a negative value
(5) Use overflow:hidden; and relative positioning, change the left, and top values to move the position of the element
(6) Cover this with a white p The p above is removed.
……
Events in js: mouse events, keyboard events, system events, form events, custom events, etc. Common mouse events include: onmouseover, onmouseout, onmousemove, onclick, onmounseup, mousedown, etc. Function calling methods: event calling, anonymous calling, direct calling.

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