如何在下拉菜单中动态选择选项？

Question

如何选择一个主题，然后根据所选主题出现时间？每个主题都有不同的时间。

 <div class="form-group">
            <label class="control-label">Subject 1:</label> <font color="red">*</font>        
            <select id="levelSbj1" name="levelSbj1" class="form-control" required="required">
              <option value="0">--Select Subject--</option> 
           <option value="1">Bahasa Malaysia</option>
            <option value="2">English</option>
            <option value="3">Mathematics</option>
            <option value="4">Science</option>
            </select> 
           </div>
        <div class="form-group">
            <label class="control-label">Time and Day:</label> <font color="red">*</font>        
            <select id="levelLvl1" name="levelLvl1" class="form-control" required="required">
              <option value="0">--Select Time and Day--</option> 
           <option value="1">10.00 - 12.00 am (Saturday)</option>
            <option value="2">2.00 - 4. 00 pm (Saturday)</option>
            <option value="3">9.00 - 11.00 am (Friday)</option>
            <option value="4">3.00 - 5. 00 pm (Friday)</option>
             <option value="5">10.00 - 12.00 am (monday)</option>
            <option value="6">2.00 - 4. 00 pm (tuesday)</option>
            <option value="7">9.00 - 11.00 am (thursday)</option>
            <option value="8">3.00 - 5. 00 pm (sunday)</option>
            </select>
            </div>

Answer 1

在客户端，您可以像这样尝试使用jQuery：