我在如何加载HTML< select>时遇到问题在首次加载页面或刷新页面时使用值.
我实际上正在尝试使用3个下拉菜单创建一个date_select,其中包括年,月和日,当月菜单或年菜单更改时,它将自动调整天数.
例如,当我选择3月份的日期为31日或4月时,日期将仅为30日.
我的问题是当页面首次加载时,日期菜单为空.我在< select>上尝试了onload但它不起作用.我是编程的初学者,所以即使是这样的简单练习我也遇到了麻烦.请帮忙.
date_select.php
<script type="text/javascript" >
function loadDays() {
var year = parseInt(document.getElementById('years').value);
var month = document.getElementById('months').value;
var months = new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");
var days = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
if ((year % 4) == 0) days[1] = 29;
var days_select = document.getElementById('days');
days_select.options.length = 0;
for(i in months) {
if (month == months[i]) {
for(var j = 1; j <= days[i]; j++ ) days_select.options[days_select.options.length] = new Option(j, j);
break;
}
}
}
</script>
<span style="display: table; ">
<span style="display: table-cell; ">
<select id="years" onchange="loadDays();">
<?php
for($year = 1900; $year <= 2100; $year++ ) {
if ($year == date('Y')) echo "<option value='$year' selected=''>" . $year . "</option>";
else echo "<option value='$year'>" . $year . "</option>";
}
?>
</select>
</span>
<span style="display: table-cell; ">
<select id="months" onchange="loadDays();">
<?php
$months = array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" );
foreach($months as $month){
if ($month == date('M')) echo "<option value='$month' selected=''> " . $month . "</option>";
else echo "<option value='$month'> " . $month . "</option>";
}
?>
</select>
</span>
<span style="display: table-cell; ">
<select id="days" onl oad="loadDays();">
</select>
</span>
</span>
解决方法:
尝试将onload属性放在body标签中而不是select标签中.
<body onl oad="loadDays();">
标签:javascript,php,html-select 来源: https://codeday.me/bug/20190726/1543163.html
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