<select data-placeholder="Please select a payment method.." style="width:50%;" class="chosen" onchange="currencyChange(this.value)">
    <option value=""></option>
    <optgroup label="Cash">
        <option value="Paypal">Paypal</option>
        <option value="Bitcoin">Bitcoin</option>
        <option value="Western Union">Western Union</option>
        <option value="Delivery">Delivery</option>
    </optgroup>
    <optgroup label="Ingame Currency">
        <option value="RS3 GP">RS3 GP</option>
        <option value="OSRS GP">OSRS GP</option>
    </optgroup>
</select>
<script type="text/javascript">
var sign = "null";
var placement = "null";
float budget = "null";
function currencyChange(data){
    if (data === 'Paypal') {
        sign = "$";
        placement = "before";
    }
    if (data === 'Bitcoin') {
        sign = "$";
        placement = "before";
    }
    if (data === 'Western Union') {
        sign = "$";
        placement = "before";
    }
    if (data === 'Delivery') {
        sign = "$";
        placement = "before";
    }
    if (data === 'RS3 GP') {
        sign = "M/GP";
        placement = "after";
    }
    if (data === 'OSRS GP') {
        sign = "M/GP";
        placement = "after";
    }
    if (placement === 'before') {                                                            
        document.getElementById("budget").value = sign + document.getElementById("budget").value;
    }
    if (placement === 'after') {                                                            
        document.getElementById("budget").value = document.getElementById("budget").value + sign;                                                            
    }
}
</script>
I am trying to change the currency type of another textfield id="budget" to add a currency symbol dependent on the choice of payment method..?
But I get no such action when selecting the payment type.