如何编写jQuery / javascript if语句，以便在html时触发 <option>选择特定班级？

Question

<select>
  <option value='34'>Trees</option>
  <option value='13' class='create_sub_category'>Add new sub-category</option>
  <option value='24' class='create_sub_category'>Add new sub-category</option>
  <option value='57'>Cats</option>
  <option value='34' class='create_sub_category'>Add new sub-category</option>
</select>



<script type='text/javascript'>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js"></script>
if (selected(".create_sub_category")) {
  alert('hi');
}
</script>

Obviously, there's no such javascript or jQuery function called 'selected' that I used above in my if statement, but could someone help me find something that would do what I'm describing?

Answer 1

$('select').change(function() {
  if($('select option:selected').hasClass('create_sub_category')) 
  {
    alert("SELECTED");
  }  
});

You should put some id/class on that select element.

Answer 2

You can do this:

if($("select option:selected").hasClass("create_sub_category")) {
  alert("hi");
}

The key here is: option:selected

Answer 3

No need for jQuery

if(/\bcreate_sub_category\b/.test(select.options[ select.selectedIndex ].className))
    //...

jsFiddle