JSFiddle - React, Tailwind, and code Playground

by Ashish

HTML

Price: <input type="text" id="price" value="100" /><br /><br />

Quantity :
<select id="qty" onchange="calculate()">
	<option value=""></option>
	<option value="1">1</option>
	<option value="2">2</option>
	<option value="3">3</option>
	<option value="4">4</option>
	<option value="5">5</option>
</select>
<br /><br />
Total : <input type="text" id="total" /><br />

<script>
function calculate()
    {
	   var price = document.getElementById("price").value;
       var qty = document.getElementById("qty").value;
	   var total = parseFloat(price) * parseFloat(qty);
	   document.getElementById("total").value = total;
    }
</script>