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HTML

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Adding Classes

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CSS

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CSS Base

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JavaScript

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Babel includes JSX processing.

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HTML 

              
                <div id="wrapper">
  <h1>Pure Javascript, HTML 5 &amp; CSS3 Tabs</h1>
  <div id="tabContainer">
    <div id="tabs">
      <ul>
        <li id="tabHeader_1">Page 1</li>
        <li id="tabHeader_2">Page 2</li>
        <li id="tabHeader_3">Page 3</li>
      </ul>
    </div>
    <div id="tabscontent">
      <div class="tabpage" id="tabpage_1">
        <h2>Page 1</h2>
        <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. 
          Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum 
          erat wisi, condimentum sed, commodo vitae, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus lacus enim ac dui.
          Donec non enim in turpis pulvinar facilisis. Ut felis. Praesent dapibus, neque id cursus faucibus, tortor neque egestas augue, eu vulputate magna eros eu erat. Aliquam erat 
          volutpat. Nam dui mi, tincidunt quis, accumsan porttitor, facilisis luctus, metus. </p>
      </div>
      <div class="tabpage" id="tabpage_2">
        <h2>Page 2</h2>
        <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. 
          Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. </p>
        <p>Vestibulum erat wisi, condimentum sed, commodo vitae, ornare sit amet, wisi. Aenean fermentum, elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus 
        lacus enim ac dui. Donec non enim in turpis pulvinar facilisis. </p>
        <p> Ut felis. Praesent dapibus, neque id cursus faucibus, tortor neque egestas augue, eu vulputate magna eros eu erat. Aliquam erat volutpat. Nam dui mi, tincidunt quis, 
        accumsan porttitor, facilisis luctus, metus. </p>
      </div>
      <div class="tabpage" id="tabpage_3">
        <h2>Page 3</h2>
        <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. </p>
        <p>Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu libero sit amet quam egestas semper. Aenean ultricies mi vitae est. Mauris 
        placerat eleifend leo. Quisque sit amet est et sapien ullamcorper pharetra. Vestibulum erat wisi, condimentum sed, commodo vitae, ornare sit amet, wisi. Aenean fermentum, 
        elit eget tincidunt condimentum, eros ipsum rutrum orci, sagittis tempus lacus enim ac dui.</p>
        <p>Donec non enim in turpis pulvinar facilisis. Ut felis. Praesent dapibus, neque id cursus faucibus, tortor neque egestas augue, eu vulputate magna eros eu erat. Aliquam 
        erat volutpat. Nam dui mi, tincidunt quis, accumsan porttitor, facilisis luctus, metus. </p>
      </div>
    </div>
  </div>
!

CSS 

              
                * {
	margin:0;
	padding:0;
}

body {
	background:url(../../images/background.png) top left;
	font: .8em "Lucida Sans Unicode", "Lucida Grande", sans-serif;
}

h2{ 
	margin-bottom:10px;
}

#wrapper{
	width:720px;
	margin:40px auto 0;
}

#wrapper h1{
	color:#FFF;
	text-align:center;
	margin-bottom:20px;
}

#wrapper a{
	display:block;
	font-size:1.2em;
	padding-top:20px;
	color:#FFF;
	text-decoration:none;
	text-align:center;
}

#tabContainer {
	width:700px;
	padding:15px;
	background-color:#2e2e2e;
	-moz-border-radius: 4px;
	border-radius: 4px; 
}

#tabs{
	height:30px;
	overflow:hidden;
}

#tabs > ul{
	font: 1em;
	list-style:none;
}

#tabs > ul > li{
	margin:0 2px 0 0;
	padding:7px 10px;
	display:block;
	float:left;
	color:#FFF;
	-webkit-user-select: none;
	-moz-user-select: none;
	user-select: none;
	-moz-border-radius-topleft: 4px;
	-moz-border-radius-topright: 4px;
	-moz-border-radius-bottomright: 0px;
	-moz-border-radius-bottomleft: 0px;
	border-top-left-radius:4px;
	border-top-right-radius: 4px;
	border-bottom-right-radius: 0px;
	border-bottom-left-radius: 0px; 
	background: #C9C9C9; /* old browsers */
	background: -moz-linear-gradient(top, #0C91EC 0%, #257AB6 100%); /* firefox */
	background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#0C91EC), color-stop(100%,#257AB6)); /* webkit */
}

#tabs > ul > li:hover{
	background: #FFFFFF; /* old browsers */
	background: -moz-linear-gradient(top, #FFFFFF 0%, #F3F3F3 10%, #F3F3F3 50%, #FFFFFF 100%); /* firefox */
	background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#FFFFFF), color-stop(10%,#F3F3F3), color-stop(50%,#F3F3F3), color-stop(100%,#FFFFFF)); /* webkit */
	cursor:pointer;
	color: #333;
}

#tabs > ul > li.tabActiveHeader{
	background: #FFFFFF; /* old browsers */
	background: -moz-linear-gradient(top, #FFFFFF 0%, #F3F3F3 10%, #F3F3F3 50%, #FFFFFF 100%); /* firefox */
	background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#FFFFFF), color-stop(10%,#F3F3F3), color-stop(50%,#F3F3F3), color-stop(100%,#FFFFFF)); /* webkit */
	cursor:pointer;
	color: #333;
}

#tabscontent {
	-moz-border-radius-topleft: 0px;
	-moz-border-radius-topright: 4px;
	-moz-border-radius-bottomright: 4px;
	-moz-border-radius-bottomleft: 4px;
	border-top-left-radius: 0px;
	border-top-right-radius: 4px;
	border-bottom-right-radius: 4px;
	border-bottom-left-radius: 4px; 
	padding:10px 10px 25px;
	background: #FFFFFF; /* old browsers */
	background: -moz-linear-gradient(top, #FFFFFF 0%, #FFFFFF 90%, #e4e9ed 100%); /* firefox */
	background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#FFFFFF), color-stop(90%,#FFFFFF), color-stop(100%,#e4e9ed)); /* webkit */
	margin:0;
	color:#333;
}
!

JS 

              
                  // get tab container
  	var container = document.getElementById("tabContainer");
		var tabcon = document.getElementById("tabscontent");
		//alert(tabcon.childNodes.item(1));
    // set current tab
    var navitem = document.getElementById("tabHeader_1");
		
    //store which tab we are on
    var ident = navitem.id.split("_")[1];
		//alert(ident);
    navitem.parentNode.setAttribute("data-current",ident);
    //set current tab with class of activetabheader
    navitem.setAttribute("class","tabActiveHeader");

    //hide two tab contents we don't need
   	 var pages = tabcon.getElementsByTagName("div");
    	for (var i = 1; i < pages.length; i++) {
     	 pages.item(i).style.display="none";
		};

    //this adds click event to tabs
    var tabs = container.getElementsByTagName("li");
    for (var i = 0; i < tabs.length; i++) {
      tabs[i].onclick=displayPage;
    }

// on click of one of tabs
function displayPage() {
  var current = this.parentNode.getAttribute("data-current");
  //remove class of activetabheader and hide old contents
  document.getElementById("tabHeader_" + current).removeAttribute("class");
  document.getElementById("tabpage_" + current).style.display="none";

  var ident = this.id.split("_")[1];
  //add class of activetabheader to new active tab and show contents
  this.setAttribute("class","tabActiveHeader");
  document.getElementById("tabpage_" + ident).style.display="block";
  this.parentNode.setAttribute("data-current",ident);
}
!
999px

Console