Javascript 根据选中的选项计算值

1. 您的 switch 语句需要在每个"案例"之后都有"break;"。

2. 无论选择什么，这总是返回 -1(未找到(：

   var current_index = cat_buttons.index(cat_buttons.find('：checked'((

这是一个工作代码：

<script type="text/javascript" src="https://code.jquery.com/jquery-2.2.0.min.js"></script>
<h2 class="contentheading" style="margin-top: 0px;">2016 “Train-The-Trainer” Workshops<br /><br /> AERIAL</h2>
<div>
    <p>$50.00 per class/person<br />Sign up for both for $90.00</p>
</div>
<div>
    <form id="paypal_submit_form" action="https://www.paypal.com/***" method="post">
        <input name="cmd" type="hidden" value="_cart" /> 
        <input name="upload" type="hidden" value="1" /> 
        <input name="charset" type="hidden" value="utf8" /> 
        <input name="business" type="hidden" /> 
        <input name="currency_code" type="hidden" value="USD" /> 
        <input name="custom" type="hidden" /> 
        <input name="amount" type="hidden" /> 
        <input name="first_name" type="hidden" /> 
        <input name="last_name" type="hidden" /> 
        <input name="address1" type="hidden" /> 
        <input name="city" type="hidden" /> 
        <input name="state" type="hidden" /> 
        <input name="zip" type="hidden" /> 
        <input name="email" type="hidden" /> 
        <input name="night_phone_b" type="hidden" /> 
        <input name="address_override" type="hidden" value="1" />
        <div id="paypal_prs" style="font-size: 12px;">
            <p>
                <input id="cat-both" checked="checked" name="cat" type="radio" value="90" />
                    <label for="cat-both">Both</label> 
                <input id="cat-aerial" name="cat" type="radio" value="50" />
                    <label for="cat-aerial">Aerial</label> 
                <input id="cat-loto" name="cat" type="radio" value="50" />
                    <label for="cat-loto">Lockout/Tagout</label>
            </p>
            <br /> Members:
            <select id="bal_number_of_members" style="font-size: 12px; padding: 3px;" name="number_of_members">
                <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>
                <option value="6">6</option>
                <option value="7">7</option>
                <option value="8">8</option>
                <option value="9">9</option>
                <option value="10">10</option>
                <option value="11">11</option>
            </select>
            <br /> Total Amount (Cost + Processing Fee): 
                <input style="width: 50px; margin-right: 10px; padding: 2px; padding-bottom: 1px; font-size: 12px;" name="tmp_total_amount" readonly="readonly" type="text" value="93" /> 
                <input id="bal_submit_btn" style="padding: 3px 5px; font-size: 12px; cursor: pointer;" type="button" value="Pay Here" /> 
                <input name="item_name_1" type="hidden" value="2016 Train-The-Trainer Workshops(AERIAL LIFTS &amp; LOCKOUT/TAGOUT)" /> 
                <input name="amount_1" type="hidden" value="90" /> 
                <input name="quantity_1" type="hidden" value="1" /> 
                <input name="item_name_2" type="hidden" value="Processing fee" /> 
                <input name="amount_2" type="hidden" value="0" /> 
                <input name="quantity_2" type="hidden" value="1" />
        </div>
        <input name="notify_url" type="hidden" value="http://some.org/tmp_ipn.php" /> 
        <input name="return" type="hidden" value="http://some.org/" /> 
        <input name="cancel_return" type="hidden" value="http://some.org/index.php?view=article&amp;id=278" /> 
        <input name="no_shipping" type="hidden" value="1" />
    </form>
</div>
<div style="font-size: 11px; margin-top: 10px; color: red;">
    Additional 2.9% + $0.30 processing fee will be charged with all orders paid by credit card.
</div>
<div style="margin-top: 50px;">
    <a style="font-size: 18px;" href="images/Flyer_2016.pdf" target="_blank">Download Order Form</a>
</div>
<p style="font-size: 14px;">
    <strong>Please fax or email the order form to the office.</strong>
</p>
<script>
function getPayPalProcessingFee() {
         var qty = jQuery('#paypal_submit_form select[name=number_of_members]').val();
         qty = parseInt(qty);
         //var cat_buttons = jQuery("input[name=cat]")
         //var current_index = cat_buttons.index(cat_buttons.find(':checked'));
         var current_index = $("input[name=cat]:checked").attr('id');
         switch (current_index){
             case 'cat-both':
                return 3*qty;
                break;
             case 'cat-aerial':
                return 0;
                break;
             case 'cat-loto':
                return 1.8*qty;
                break;
             default:
                return 0;
         }
     }
    function trainthetrainerForm_calculateItemAmount() {
        var qty = jQuery('#paypal_submit_form select[name=number_of_members]').val();
        var current_val = jQuery("input[name=cat]:checked").val();
        var amount = parseInt(qty) * current_val;
        amount = parseFloat(amount).toFixed(2);
        return amount;
    }
    function trainthetrainerForm_calculateFee() {
        var fee = getPayPalProcessingFee();
        return fee;
    }
    function trainthetrainerForm_displayTotalAmount() {
        var amount = trainthetrainerForm_calculateItemAmount();
console.log(amount);        
        var fee = getPayPalProcessingFee();
console.log(fee);        
        var totalamount = parseFloat(amount) + parseFloat(fee);
console.log(totalamount);        
        totalamount = parseFloat(totalamount).toFixed(2);
console.log(totalamount);
        jQuery('#paypal_submit_form input[name=tmp_total_amount]').val(totalamount);
    }
    function submitTrainthetrainerForm() {
        var qty = jQuery('#paypal_submit_form select[name=number_of_members]').val();
        jQuery('#paypal_submit_form input[name=quantity_1]').val(qty);
        var totalAmount = 0;
        var amount = trainthetrainerForm_calculateItemAmount();
        var processingFee = trainthetrainerForm_calculateFee();
        totalAmount = amount + processingFee;
        jQuery('#paypal_submit_form input[name=business]').val('shana@same.org');
        jQuery('#paypal_submit_form input[name=amount]').val(totalAmount);
        jQuery('#paypal_submit_form input[name=amount_2]').val(processingFee);
        jQuery('#paypal_submit_form').submit();
        return true;
    }
    jQuery(document).ready(function (){
        $(document).on('change',$("#bal_number_of_members"),function(){
            trainthetrainerForm_displayTotalAmount();
        });
        jQuery("#bal_submit_btn").click(function() {
            submitTrainthetrainerForm();
        });
        trainthetrainerForm_displayTotalAmount();
    });
</script>