我只是想解释一下:
if ($('.combo option:selected[value==0]'))
要检查下拉列表中的选定项目是否为 0,您可以使用以下命令:
if ($('.combo').val() == '0') // simpler and more readable :-)
然后,如果您已经将错误消息放在文档中的某个位置,它会更简单。您需要做的就是显示/隐藏它。例如:
<select id="dropdown-1" class="combo">
<option value="0">-</option>
<option value="1">Lorem</option>
<option value="2">Ipsum</option>
</select>
<span id="error-dropdown-1" class="error" style="display: none">Please select a value!</span> <!-- hidden by default. can also use CSS instead of style="display: none" -->
<input type="button" id="demo-button" value="Demo" />
和javascript(+ jquery):
$('#demo-button').click(function() {
if ($('.combo').val() == '0') {
$('#error-dropdown-1').show();
} else {
$('#error-dropdown-1').hide();
}
});
这是另一个例子。如果您避免使用 ID(也许您已经动态生成了 dorpdowns),则很有用:
<script type="text/javascript">
$(function() {
$('#demo-button').click(function() {
$('.combo').each(function() {
var div = $(this).parents('div').get(0); // get the wrapper
if ($(this).val() == '0') {
$(div).find('.error').show(); // show <span class=".error"> inside the wrapper
} else {
$(div).find('.error').hide(); // hide <span class=".error"> inside the wrapper
}
});
});
});
</script>
<div> <!-- wrapper for 1st combo + 1st error message -->
<select class="combo">
<option value="0">-</option>
<option value="1">Lorem</option>
<option value="2">Ipsum</option>
</select>
<span class="error" style="display: none">Please select a value!</span>
</div>
<div> <!-- wrapper for 2nd combo + 2nd error message -->
<select class="combo">
<option value="0">-</option>
<option value="1">Dolor</option>
<option value="2">Sit</option>
<option value="3">Amet</option>
</select>
<span class="error" style="display: none">Please select a value!</span>
</div>
<div> <!-- wrapper for 3rd combo + 3rd error message -->
<select class="combo">
<option value="0">-</option>
<option value="1">Consectetuer</option>
<option value="2">Adipiscing</option>
<option value="3">Elit</option>
</select>
<span class="error" style="display: none">Please select a value!</span>
</div>
<input type="button" id="demo-button" value="Demo" />