JavaScript functions

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Why the hell wont my function work when called????



<script type="text/javascript">

    function calcTotal(){

    var extra1 = 0;
    var extra2 = 0;
    var extra3 = 0;
    var option1 = 0;
    var total = 0;

    //check to see which option button is checked
    if (document.details.optionGroup[0].checked {
        option1 = document.details.optionGroup[0].value
    }
    else if (document.details.optionGroup[1].checked {
        option1 = document.details.optionGroup[1].value
    }
    else if (document.details.optionGroup[2].checked {
        option1 = document.details.optionGroup[2].value
    }
    else
    {
        option = 0;
    }

   
        //check to see which checkboxes are checked
        if (document.details.extra1.checked){
            extra1=150;
        }//end of if
        if (document.details.extra2.checked){
            extra2=100;
        }//end of if
        if (document.details.extra3.checked){
            extra3=250;
        }//end of if

    total =parseInt(option1) + parseint(extra1) + parseInt(extra2) + parseInt(extra3);

    incvat=Math.round((total/100)*121);

    document.details.exvat.value = total;
    document.details.incvat.value = incvat;
    }//End of calcTotal Function