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Sample code sharing on how to implement multi-level menu effects using JavaScript

黄舟Original: 2017-07-26 16:07:441689browse

The example in this article shares with you the specific code for realizing multi-level menu effect display in js for your reference. The specific content is as follows

The specific code is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Document</title>
  <style>
    *{
      margin:0;
      padding:0;
      font-size:14px;
    }
    ul,li{
      list-style:none;
    }
    .box{
      margin:10px;
      padding:10px;
      width:300px;
      border:1px dashed #008000;
      /*渐进增强:首先设置一个纯色的背景，对于不兼容css3的浏览器来说会使用纯色，对于兼容的浏览器，我们在下面在额外的增加一些渐变色，这样会覆盖掉上面*/
      background:#ffe470;
      background:-webkit-linear-gradient(top left,#2b93d2,#fa5889,#cde074,#ffe470);
      background:-moz-linear-gradient(top left,#2b93d2,#fa5889,#cde074,#ffe470);
      background:-o-linear-gradient(top left,#2b93d2,#fa5889,#cde074,#ffe470);
      background:linear-gradient(top left,#2b93d2,#fa5889,#cde074,#ffe470);
    }
    .box li{
      position:relative;
      line-height:30px;
    }
    .box em{
      position:absolute;
      top:7px;
      left:0;
      width:16px;
      height:16px;
      background:url("img/icon.png") no-repeat -59px -28px;
      cursor:pointer;

    }
    .box span{
      display:block;
      padding-left:20px;
    }
    .box em.open{
      background-position:-42px -28px;
    }
    .box .two{
      margin-left:20px;
    }
    .box .three{
      margin-left:40px;
    }
    .box .four{
      margin-left:60px;
    }
    .box .two,.box .three,.box .four{
      display:none;
    }
  </style>
</head>
<body>
  <p class=&#39;box&#39; id=&#39;box&#39;>
    <ul>
      <li>
        <em></em>
        <span>第一级第一个</span>
        <ul class=&#39;two&#39;>
          <li><span>第二级第一个</span></li>
          <li>
            <em></em><span>第二级第二个</span>
            <ul class=&#39;three&#39;>
              <li><span>第三极第一个</span></li>
              <li><span>第三极第二个</span></li>
              <li>
                <em></em><span>第三极第三个</span>
                <ul class=&#39;four&#39;>
                  <li><span>第四级第一个</span></li>
                  <li><span>第四级第二个</span></li>
                  <li><span>第四级第三个</span></li>
                </ul>
              </li>
            </ul>
          </li>
          <li>
            <em></em><span>第二级第三个</span>
            <ul class=&#39;three&#39;>
              <li><span>第三级第一个</span></li>
              <li><span>第三级第二个</span></li>
              <li><span>第三级第三个</span></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
    <ul>
      <li>
        <em></em>
        <span>第一级第一个</span>
        <ul class=&#39;two&#39;>
          <li><span>第二级第一个</span></li>
          <li>
            <em></em><span>第二级第二个</span>
            <ul class=&#39;three&#39;>
              <li><span>第三极第一个</span></li>
              <li><span>第三极第二个</span></li>
              <li>
                <em></em><span>第三极第三个</span>
                <ul class=&#39;four&#39;>
                  <li><span>第四级第一个</span></li>
                  <li><span>第四级第二个</span></li>
                  <li><span>第四级第三个</span></li>
                </ul>
              </li>
            </ul>
          </li>
          <li>
            <em></em><span>第二级第三个</span>
            <ul class=&#39;three&#39;>
              <li><span>第三级第一个</span></li>
              <li><span>第三级第二个</span></li>
              <li><span>第三级第三个</span></li>
            </ul>
          </li>
        </ul>
      </li>
    </ul>
  </p>

  <script>
    var box = document.getElementById(&#39;box&#39;);
    //把列表中的span(前面有em的span)设置一个 cursor:pointer的样式
    var spanList = box.getElementsByTagName("span");
    for(var i = 0;i<spanList.length;i++){
      var curSpan = spanList[i];
      var curPre = utils.prev(curSpan);
      if(curPre && curPre.tagName.toLowerCase()==="em"){
        curSpan.style.cursor = "pointer"
      }

    }
    //使用事件委托实现我们的操作
    box.onclick = function(e){
      e = e || window.event;
      var tar = e.target || e.srcElement;

      //只有点击的是em或者span标签，我们才进行展开收缩的操作
      if(/^(em|span)$/i.test(tar.tagName)){
        var parent = tar.parentNode;//获取父亲
        var firstUl = utils.children(parent,"ul")[0]//获取父亲子集中的第一个ul标签
        var oEm = utils.children(parent,"em")[0]
        if(firstUl){
          //如果隐藏让显示，否则让隐藏
          var isBlock = utils.getCss(firstUl,"display") === "block" ? true : false;
          if(isBlock){
            firstUl.style.display = "none";
            if(oEm){
              utils.removeClass(oEm,"open")
            }
            //当外层的收起，里层所有的ul都要隐藏，所有的em都要移除open样式
            var allUl = parent.getElementsByTagName("ul"),allEm = parent.getElementsByTagName("em");
            for(var i = 0;i<allUl.length;i++){
              allUl[i].style.display = "none";
              utils.removeClass(allEm[i],"open");
            }
          }else{
            firstUl.style.display = "block";
            if(oEm){
              utils.addClass(oEm,"open")
            }
          }
        }

      }
    }
  </script>
</body>
</html>

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