Love Calculator Using JavaScript HTML and CSS With Code to Find Love Percentage

<!DOCTYPE html>
<html>
<head>
<title></title>

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css">

<style >
body{
background-image: linear-gradient(rgba(0,0,0,0.3),rgba(0,0,0,0.3)), url('https://images.pexels.com/photos/1028725/pexels-photo-1028725.jpeg');
background-repeat: no-repeat;
background-position: center;
background-size: cover;
width: 100%;
height: 100vh;
position: relative;
}
header{
width: 100%;
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%, -50%);
}
</style>
</head>
<body>

<header >

<div class="card w-50 m-auto text-center ">
<div class="card-header bg-danger text-white">LOVE CALCULATOR</div>
<div class="card-body">
<form class="form-inline w-75 m-auto">
<div class="form-group">
<input type="text" name="" class="form-control text-center" placeholder="Your Name" id="name" >
</div>
<div class="pl-4 pr-4">
<span> + </span>
</div>
<div class="form-group">
<input type="text" name="" class="form-control text-center" placeholder=" Love Name" id="lname">
</div>
</form> <br>
<div class="w-70 m-auto">
<button class="btn btn-success w-50" onclick="checkloveper()"> click </button>
</div>
<br>
<div>
<input type="text" name="" placeholder="LOVE PERCENTAGE" class="form-control text-center w-25 m-auto" id="lovevalue">
</div>
</div>
<div class="card-footer ">God Bless Your RelationShip</div>
</div>

</header>

<script>
function checkloveper(){

var name = document.getElementById('name').value;
var lname = document.getElementById('lname').value;

if(name == ""){
alert('Please enter your name');
}else if (name.length <=2 ) {
alert('Min lenght is 3')
}else if(!isNaN(name)){
alert('Numbers are not allowed');
}

else if(lname == ""){
alert('Please enter your love name');
}else if (lname.length <=2 ) {
alert('Min lenght is 3')
}else if(!isNaN(lname)){
alert('Numbers are not allowed');
}
else{
var lovdata = Math.random() * 100;
lovdata = Math.floor(lovdata);
document.getElementById('lovevalue').value = lovdata + "%";
}

}
</script>
</body>

</html>