document-object1.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script type="text/javascript">  
        function getcube(){  
        var number=document.getElementById("number").value;  
        document.writeln(number*number*number);  
        }  
        </script>  
        <form>  
        Enter No:<input type="text" id="number" name="number"/> 
        <input type="button" value="cube" onclick="getcube()"/>  
        </form>  
</body>
</html>