<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>
<input type="text" id="insert">
<button onclick="add()">Add</button>
<ul id="demo">
</ul>
<script>
var lk=""
for (var i=10;i<=50;i++){
lk+=i+"<br>"
i+=1;
}
document.getElementById('demo').innerHTML=lk
</script>
</body>
</html>
