function openCity(evt, cityName) {
var i, tabcontent, tablinks;
tabcontent = document.getElementsByClassName(“tabcontent”);
for (i = 0; i < tabcontent.length; i++) {
tabcontent[i].style.display = “none”;
}
tablinks = document.getElementsByClassName(“tablinks”);
for (i = 0; i < tablinks.length; i++) {
tablinks[i].className = tablinks[i].className.replace(” active”, “”);
}
document.getElementById(cityName).style.display = “block”;
evt.currentTarget.className += ” active”;
}

// Get the element with id=”defaultOpen” and click on it
document.getElementById(“defaultOpen”).click();

body {
font-family: Arial;
}

.tab {
overflow: hidden;
border: 1px solid #ccc;
background-color: #f1f1f1;
}

.tab button {
background-color: inherit;
float: left;
border: none;
outline: none;
cursor: pointer;
padding: 14px 16px;
transition: 0.3s;
font-size: 17px;
}

.tab button:hover {
background-color: #ddd;
}

.tab button.active {
background-color: #ccc;
}

.tabcontent {
display: none;
padding: 6px 12px;
border: 1px solid #ccc;
border-top: none;
}

Click on the buttons inside the tabbed menu: