php - 使用 javascript 使用单个选择框控制多选框

Question

`<select multiple="multiple" name="state[]" id="state">
<option value="">Select a State</option>
<?php 
foreach($state_list as $key=>$value){
echo "<option value=\"$key\"";
if($html['state']==$key|| $row['state']==$key){
echo ' selected="selected"';
}
echo ">$value</option>\n";                                     
}?>
</select> </p>`


<p>Select A Country
<select name="country" id="country">
<option value="0">Select a Country</option>
<option value="USA">USA</option>                             
<option value="UK">UK</option>    
</select> </p>

我有两个选择框 1)state[] 2) Country 。想要的是“如果所选国家不是美国，则禁用包含所有美国州的多选框”。感谢任何帮助

Answer 1

将此 Javascript 添加到您的代码中:

<script type="text/javascript">
<!--
window.onload = function() {
    var selectCountry = document.getElementById('country');
    selectCountry.onchange = function() {
        document.getElementById('state').disabled = (selectCountry.value != 'USA')? true : false;
    };
};
//-->
</script>