javascript，如果复选框的条件仅起作用一次

Question

I am fairly new to javascript programming and just can't seem to get this right even after going through the questions here, basically i have a checkbox which displays two radio buttons only when it is unselected

<span><strong>Not Available</strong></span>
<input  type="checkbox" placeHolder="" id="available" style="" name="available" required value="Yes"/>
<span style=" visibility: hidden; " id="BACSSpan">BACS</span><input type="radio" id="BACS" name="paymentSpecified" value="BACS" style="visibility: hidden;">
<span style="visibility: hidden;" id="ChequeSpan">Cheque</span> <input type="radio" id="Cheque" name="paymentSpecified"  value="Cheque" style=visibility: hidden;">

I have used the following javascript:

$('body').on('click', '#available', function ()
  {
    if ($('#available:checked'))
    {
      $('#BACSSpan').css('visibility','hidden');
      $('#BACS').css('visibility','hidden');
      $('#ChequeSpan').css('visibility','hidden');
      $('#Cheque').css('visibility','hidden');
    } else 
    {
      $('#BACSSpan').css('visibility','visible');
      $('#BACS').css('visibility','visible');
      $('#ChequeSpan').css('visibility','visible');
      $('#Cheque').css('visibility','visible');
    }
  }) 

What it should do is alternate between showing the two radio buttons, but it is not doing anything, but when i reverse the order of the condition ie opposite of what i want; then the required functionality happens once only

Answer 1

The thing is that $('#available:checked') is a jQuery object - not a bool value. To get bool value you should do:

if ($(this).is(':checked')) {
    ...
}
else {
    ...
}

Answer 2

If you don't want to change your code a lot, you can simply add .length .

if ($('#available:checked').length) {
    //Do Something
}