<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!DOCTYPE html>
<html>
<body>
<h2>My First Web Page</h2>
<p>My first paragraph.</p>
<p id="show"></p>
<script>
for(var i=1;i<10;i++){
for(var j=1;j<=i;j++){
if(i==j)
document.getElementById('show').innerHTML+="*";
else
document.getElementById('show').innerHTML+=" _";
}
document.getElementById('show').innerHTML+="<br/> ";
}
for(var i=10;i>=1;i--){
for(var j=1;j<=i;j++){
if(i==j)
document.getElementById('show').innerHTML+="*";
else
document.getElementById('show').innerHTML+=" _";
}
document.getElementById('show').innerHTML+="<br/> ";
}
</script>
