<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<body>
<style>
.blue{
background:red;
}
</style>
<h2>My First JavaScript</h2>
<div onclick="lav(this)" name="division" id="one">1</div>
<div id="two" name="division" onclick="lav(this)">2</div>
<div id="three" name="division" onclick="lav(this)">3</div>
<script>
function lav(ths){
var alldiv=document.getElementsByName('division');
for(var i=0;i<alldiv.length;i++){
alldiv[i].className=''
}
ths.className='blue';
}
</script>
</body>
</html>
