Checking a text field when it was shown using jQuery form rules

Question

I have a form that generates a text box when the user selects "others" in the drop-down list.

The dynamic generation of the text field was created, and I can get the value of the text field "others".

But my problem

1) I want to check the contents of the text box when it was shown.

How to validate any offers.

<form name="f2" id="f2" method="post" action="" enctype="multipart/form-data">
    Type:
    <select name="type"  id="type" onchange='CheckColors(this.value);'> 
        <option value="1">1</option>
        <option value="2">2</option>
        <option value="3">3</option>
        <option value="others">others</option>
    </select>
    <input type="text" name="others" id="others" style='display:none;'/>
    <input type="submit" name="submit"/>
</form>

// Here is a script to validate the form. I want to check another text box when it appears only ... How to do this?

<script type = "text/javascript">
$(document).ready(function () {
    $("#f2").validate({
        debug: false,
        rules: {
            type: {
                required: true
            },
            others: {
                required: true
            },
            messages: {
                //messages for required
            }
        });
    }); 
</script>

I tried the process described above, but it always shows that they were served twice side by side.

Answer 1

$(document).ready(function () {
  $("#f2").validate({
    debug: false,
    rules: {
      type: {
        required: true
      },
      messages: {
        //messages for required
      }
    }
  });
});  

function CheckColors(value) {
  if(value=='others') {
    $('#others').show().attr('required','required');
  } else {
    $('#others').hide().removeAttr('required');
  }
}

,

others: {
   required: true
}

DEMO