javascript - jQuery 获取选择选项值为空

Question

<select name="category" id="category">
    <option value="">All Category</option>
    <option value="1">Category 1</option>
    <option value="2">Category 2</option>
    <option value="3">Category 3</option>
</select>

如何选择value=""的类别

正确的条件:

if($('#category option:selected')){
    var category_url = "&category="+$('#category').val();    
    <!-- True -->
}

条件2错误:

if($('#category option[value=""]')){
    var category_url = "";                              
    <!-- Error  -->
}

Answer 1

if(!$("#category").val())
     //selected valule is ""