错误：使用JQuery从列表中选择单选按钮

Question

我有一个代码，我在其中使用.prop（）方法选择单选按钮。问题是某个时候未选择第二个方法（付款方式），脚本崩溃并显示错误，因为这是我用来选择单选按钮的代码。

/**
 * Select shipping method when selected from the list
 */
$(document).ready(function() {
    var $options = $('.shipping-method .item');

    $options.click(function(e) {
        var $current = $(this);
        e.preventDefault()
        e.stopPropagation()
        $options.removeClass('on')
        $current.addClass('on')
        $('input', $current).prop('checked', true)
    })
})
/**
 * Select payment method when selected from the list
 */
$(document).ready(function() {
    var $options = $('.payment-method .item');

    $options.click(function(e) {
        var $current = $(this);
        e.preventDefault()
        e.stopPropagation()
        $options.removeClass('on')
        $current.addClass('on')
        $('input', $current).prop('checked', true)
    })
})

HTML

<ul>
<li>
    <div class="item"><a href="javascript:;" class="shipping_3">Home Delivery</a>
        <input name="shipping" type="radio" class="radio" id="shipping_3" value="3" checked="checked" supportcod="1" insure="0" onclick="selectShipping(this)">
    </div>
</li>
<li>
    <div class="item"><a href="javascript:;" class="shipping_8">Self-pickup</a>
        <input name="shipping" type="radio" class="radio" id="shipping_8" value="8" supportcod="1" insure="0" onclick="selectShipping(this)">
    </div>
</li>