tabs.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Tabs</title>
    <style>
        /* Style the tab  */
        .tab{
            overflow: hidden;
            border: 1px solid #ccc;
            background-color: #f1f1f1;
        }
        /* Style the buttons   */
        .tab button{
            background-color: inherit;
            float: left;
            border: none;
            outline: none;
            cursor: pointer;
            padding: 14px 16px;
            transition: 0.3s;
        }
        /* Change hover effect on buttons  */
        .tab button:hover{
            background-color: #ddd;
        }
        /* Create an active/current tablink class  */
        .tab button.active{
            background-color: #ccc;
        }
        /* Style the tab content  */
        .tabcontent{
            display: none;
            padding: 6px 12px;
            border: 1px solid #ccc;
            border-top: none;
        }
    </style>
  </head>
  <body>
    <!-- Tab links  -->
    <div class="tab">
      <button class="tablinks" onclick="openCity(event, 'London')">
        London
      </button>
      <button class="tablinks" onclick="openCity(event, 'Paris')">Paris</button>
      <button class="tablinks" onclick="openCity(event, 'Tokyo')">Tokyo</button>
    </div>

    <!-- Tab Content  -->
    <div id="London" class="tabcontent">
        <h3>London</h3>
        <p>London is the capital city of England.</p>
    </div>
    <div id="Paris" class="tabcontent">
        <h3>Paris</h3>
        <p>Paris is the capital of France.</p>
    </div>
    <div id="Tokyo" class="tabcontent">
        <h3>Tokyo</h3>
        <p>Tokyo is the capital of Japan.</p>
    </div>

    <script>
        function openCity(evt, cityName){
            // Declare all variables 
            var i, tabcontent, tablinks;

            // Get all elements with class="tabcontent" and hide them 
            tabcontent = document.getElementsByClassName("tabcontent");
            for(i=0;i<tabcontent.length;i++){
                tabcontent[i].style.display = "none";
            }

            // Get all elements with class="tablinks" and remove the class "active"
            tablinks = document.getElementsByClassName("tablinks");
            for(i=0;i<tablinks.length;i++){
                tablinks[i].className=tablinks[i].className.replace(" active","");
            }

            // Show the current tab, and add an "active" class to the button that opened the tab 
            document.getElementById(cityName).style.display = "block";
            evt.currentTarget.className+=" active";
        }
    </script>
  </body>
</html>