Javascript - potrebna pomoć početniku

Code:

<html>
    <head>
        <script language = "JavaScript">
            function izracunaj(){
                var x = document.getElementById('brojevi').options[document.getElementById('brojevi').selectedIndex].text;
                x = parseInt(x);
                
                y = parseInt(document.getElementById('broj').value);
                
                z = x*y;
                
                document.getElementById('iznos').value = z;
            }
        </script>
    </head>
    
    <body>
    
        <p>
        <select id = "brojevi">
            <option>1</option>
            <option>2</option>
            <option>3</option>
            <option>4</option>
            <option>5</option>
            <option>6</option>
            <option>7</option>
            <option>8</option>
            <option>9</option>
            <option>10</option>
        </select>
        &nbsp; Pomnozi sa: <input type = "text" id = "broj" size = "3" /> &nbsp; <input type = "button" onClick = "izracunaj()" value = "Izracunaj" />
        </p>
        
        <p><input type = "text" id = "iznos" /></p>
        
    </body>
</html>

Code:

function napuniSelect(){
   var opcije = document.getElementById("brojevi").options;
   for (i=1; i<=30; i++){
      opcije[i-1]= new Option();
      opcije[i-1].innerHTML = i;
   }
}

Code:

var x = document.getElementById('brojevi').value;
......

<option value="1">1</option>
<option value="2">2</option>
....