我有两个下拉菜单,包括年龄,年龄和年龄。这些下降中的值范围为17-50。
如果从第一个下拉菜单开始,用户选择25
,那么在第二个框中,用户可以选择一个低于理想值的值,也不会有意义。有没有办法让第二次下拉从第一次下拉选择后开始?因此,如果用户从第一个下拉列表中选择年龄25
,则第二个下拉列表将从26
开始。
正如进一步检查一样,用户可以先进入第二个下拉菜单,选择一个会使上述检查无效的选项。在这种情况下,是否还有一种方法只能在选择第一个之后启用第二次下拉?
以下是我的下拉定义:
Age from:
<select>
<option value="none"></option>
<?php
for ($i=17; $i<=50; $i++)
{
?>
<option value="<?php echo $i;?>"><?php echo $i;?></option>
<?php
}
?>
</select>
to:
<select>
<option value="none"></option>
<?php
for ($i2=18; $i2<=50; $i2++)
{
?>
<option value="<?php echo $i2;?>"><?php echo $i2;?></option>
<?php
}
?>
</select>
答案 0 :(得分:0)
请尝试以下代码:
From:
<select id='select1'>
<option value="none" SELECTED>Select an Age</option>
<option value="5">5</option>
<option value="7">7</option>
<?php
for ($i=17; $i<=50; $i++)
{
?>
<option value="<?php echo $i;?>"><?php echo $i;?></option>
<?php
}
?>
</select>
To:
<select id='select2'>
<option value="none">Select an Age</option>
</select>
<script>
var sel1 = document.getElementById('select1');
var sel2 = document.getElementById('select2');
sel1.onchange = function(event)
{
var age = sel1.value|0;
var max_age = 90;
for(var i=sel2.options.length-1;i>0;--i)
{
sel2.remove(i);
}
if(age === 0 || isNaN(age) === true)
return;
for(var i=age;i<=max_age;++i)
{
var opt = document.createElement('option');
opt.text = i;
opt.value = i;
sel2.add(opt);
}
}
</script>
答案 1 :(得分:0)
试试这个,你不能没有另一个:
Age from:
<select id="age_a" onchange="checkages_a()">
<option value="none"></option>
<?php
for($i = 17; $i <= 49; ++$i) {
echo "\t", '<option value="', $i, '">', $i, '</option>', "\n";
}
?>
</select>
to:
<select id="age_b" onchange="checkages_b()">
<option value="none"></option>
<?php
for($i = 18; $i <= 50; ++$i) {
echo "\t", '<option value="', $i, '">', $i, '</option>', "\n";
}
?>
</select>
版本A
<script type="text/javascript">
var age_a = document.getElementById("age_a");
var age_b = document.getElementById("age_b");
function checkages_a() {
var a = typeof(age_a.options[age_a.selectedIndex]) !== 'undefined' ? age_a.options[age_a.selectedIndex].value : 0;
var b = typeof(age_b.options[age_b.selectedIndex]) !== 'undefined' ? age_b.options[age_b.selectedIndex].value : 0;
if(b == 'none' || a > b)
age_b.selectedIndex = age_a.selectedIndex - 1;
}
function checkages_b() {
var a = typeof(age_a.options[age_a.selectedIndex]) !== 'undefined' ? age_a.options[age_a.selectedIndex].value : 0;
var b = typeof(age_b.options[age_b.selectedIndex]) !== 'undefined' ? age_b.options[age_b.selectedIndex].value : 0;
if(!b || b == 'none')
age_b.selectedIndex = age_a.selectedIndex - 1;
if(a == 'none' || b < a)
age_a.selectedIndex = age_b.selectedIndex + 1;
}
</script>
版本B
<script type="text/javascript">
var age_a = document.getElementById("age_a");
var age_b = document.getElementById("age_b");
function checkages_a() {
var a = typeof(age_a.options[age_a.selectedIndex]) !== 'undefined' ? age_a.options[age_a.selectedIndex].value : 0;
var b = typeof(age_b.options[age_b.selectedIndex]) !== 'undefined' ? age_b.options[age_b.selectedIndex].value : 0;
if(b == 'none' || a >= b)
age_b.selectedIndex = age_a.selectedIndex;
}
function checkages_b() {
var a = typeof(age_a.options[age_a.selectedIndex]) !== 'undefined' ? age_a.options[age_a.selectedIndex].value : 0;
var b = typeof(age_b.options[age_b.selectedIndex]) !== 'undefined' ? age_b.options[age_b.selectedIndex].value : 0;
if(!b || b == 'none')
age_b.selectedIndex = age_a.selectedIndex;
if(a == 'none' || b <= a)
age_a.selectedIndex = age_b.selectedIndex;
}
</script>