simple calculator

<!DOCTYPE html>
<html>
<head>
<title>Page Title</title>
<script>


setInterval(function(v1 , op , v2 , out){
 v1 = document.getElementById("v1");
 op = document.getElementById("op");
 v2 = document.getElementById("v2");
 out = document.getElementById("out");
 if(op.value == '+')
{
out.textContent = parseInt(v1.value) + parseInt(v2.value);
}
else if(op.value == '-'){
out.textContent = parseInt(v1.value) - parseInt(v2.value);
}
else if(op.value == 'x'){
out.textContent = parseInt(v1.value) * parseInt(v2.value);
}
else if(op.value == '/'){
out.textContent = parseInt(v1.value) / parseInt(v2.value);
}
console.log(v1)
},1);

</script>
<style>
input{width: 80px;text-align:center;}
#op{width: 40px;text-align:center;}
</style>
</head>
<body>

<input type="text" id="v1" >
<select id="op">
<option>+</option>
<option>-</option>
<option>x</option>
<option>/</option>
</select>
<input type="text" id="v2">
<b> = <span id="out"></span> </b>

</body>
</html>