JavaScript实现Tab标签页切换的最简便方式(4种)

<div class="tab-head">
      <h2 id="tab1" onmouseover="changeTab1()" class="selected">1</h2>
      <h2 id="tab2" onmouseover="changeTab2()">2</h2>
      <h2 id="tab3" onmouseover="changeTab3()">3</h2>
    </div>
    <div class="tab-content">
      <div id="c1" class="show">content1</div>
      <div id="c2">content2</div>
      <div id="c3">content3</div>
    </div>

h2 {
        border-top: solid cornflowerblue 1px;
        border-left: solid cornflowerblue 1px;
        width: 50px;
        height: 25px;
        margin: 0;
        float: left;
        text-align: center;
      }
      
      .tab-content {
        border: solid cornflowerblue 1px;
        width: 152px;
        height: 100px;
      }
      
      .tab-content div{
        display: none;
      }
      
      .selected {
        background-color: cornflowerblue;
      }
      
      .tab-content .show{
        display: block;
      }

var tab1 = document.getElementById('tab1'),
        tab2 = document.getElementById('tab2'),
        tab3 = document.getElementById('tab3'),
        c1 = document.getElementById('c1'),
        c2 = document.getElementById('c2'),
        c3 = document.getElementById('c3');

      function changeTab1() {
        tab1.className = 'selected';
        tab2.className = '';
        tab3.className = '';
        c1.className = 'show'
        c2.className = '';
        c3.className = '';
      }

      function changeTab2() {
        tab1.className = '';
        tab2.className = 'selected';
        tab3.className = '';
        c1.className = '';
        c2.className = 'show';
        c3.className = '';
      }

      function changeTab3() {
        tab1.className = '';
        tab2.className = '';
        tab3.className = 'selected';
        c1.className = ''
        c2.className = '';
        c3.className = 'show';
      }

<div class="tab-head">
      <h2 onmouseover="changeTab(0)" class="selected">1</h2>
      <h2 onmouseover="changeTab(1)">2</h2>
      <h2 onmouseover="changeTab(2)">3</h2>
    </div>
    <div class="tab-content">
      <div class="show">content1</div>
      <div>content2</div>
      <div>content3</div>
    </div>

var tabs = document.getElementsByClassName('tab-head')[0].getElementsByTagName('h2'),
        contents = document.getElementsByClassName('tab-content')[0].getElementsByTagName('div');

      function changeTab(index) {
        for(var i = 0, len = tabs.length; i < len; i++) {
          if(i === index) {
            tabs[i].className = 'selected';
            contents[i].className = 'show';
          }else{            tabs[i].className = '';
            contents[i].className = '';          }
        }
      }

<div class="tab-head">
      <h2 onmouseover="changeTab(this)" class="selected">1</h2>
      <h2 onmouseover="changeTab(this)">2</h2>
      <h2 onmouseover="changeTab(this)">3</h2>
    </div>
    <div class="tab-content">
      <div class="show">content1</div>
      <div>content2</div>
      <div>content3</div>
    </div>

var tabs = document.getElementsByClassName('tab-head')[0].getElementsByTagName('h2'),
        contents = document.getElementsByClassName('tab-content')[0].getElementsByTagName('div');

      function changeTab(tab) {
        for(var i = 0, len = tabs.length; i < len; i++) {
          if(tabs[i] === tab) {
            tabs[i].className = 'selected';
            contents[i].className = 'show';
          } else {
            tabs[i].className = '';
            contents[i].className = '';
          }
        }
      }

<div class="tab-head">
      <h2 class="selected">1</h2>
      <h2>2</h2>
      <h2>3</h2>
    </div>
    <div class="tab-content">
      <div class="show">content1</div>
      <div>content2</div>
      <div>content3</div>
    </div>

var tabs = document.getElementsByClassName('tab-head')[0].getElementsByTagName('h2'),
        contents = document.getElementsByClassName('tab-content')[0].getElementsByTagName('div');

      (function changeTab(tab) {
        for(var i = 0, len = tabs.length; i < len; i++) {
          tabs[i].onmouseover = showTab;
        }
      })();

      function showTab() {
        for(var i = 0, len = tabs.length; i < len; i++) {
          if(tabs[i] === this) {
            tabs[i].className = 'selected';
            contents[i].className = 'show';
          } else {
            tabs[i].className = '';
            contents[i].className = '';
          }
        }
      }