Javascript Section of Website

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";
}
<button class="tablinks" onclick="openCity(event, 'About')" id="defaultOpen">About</button>

{ <script>
// Get the element with id="defaultOpen" and click on it
document.getElementById("defaultOpen").click();
</script> }