Php JavaScript3下拉菜单。更改一个下拉菜单时，为其他两个下拉菜单设置默认值。需要优化

代码很长。但从我的观点来看，为了说明什么是必要的，我必须发布整个代码

三个下拉菜单。使用Php和javascript。如果在其中一个菜单中更改值，则其他两个菜单中的值设置为默认值

创建了需要改进/优化的长代码（缩短代码需要javascript）

在这里发布代码（没有php）（由于不可理解的原因，在JSFIDLE中发布的代码不能完全工作；在我的网站上，代码按预期工作。）

首先是php

$options_month = array("Select month", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December");
$options_quarter = array("Select quarter", "First", "Second", "Third", "Fourth");
$options_halfyear = array("Select half-year", "First", "Second");

然后是下拉菜单

<select id="month_id" name="monthid">
<?php
foreach ( $options_month as $i1=>$opt1 ) : 
echo '<option value="' .htmlspecialchars($i1) .'"' .((htmlspecialchars($i1) == htmlspecialchars($_POST['monthid'][$counter]))? 'selected' : "") .'>'.htmlspecialchars($opt1) .'</option>';
endforeach;
?>
</select>

<select id="quarter_id" name="quarterid">
<?php
foreach ( $options_quarter as $i1=>$opt1 ) : 
echo '<option value="' .htmlspecialchars($i1) .'"' .((htmlspecialchars($i1) == htmlspecialchars($_POST['quarterid'][$counter]))? 'selected' : "") .'>'.htmlspecialchars($opt1) .'</option>';
endforeach;
?>
</select>

<select id="halfyear_id" name="halfyearid">
<?php
foreach ( $options_halfyear as $i1=>$opt1 ) : 
echo '<option value="' .htmlspecialchars($i1) .'"' .((htmlspecialchars($i1) == htmlspecialchars($_POST['halfyear'][$counter]))? 'selected' : "") .'>'.htmlspecialchars($opt1) .'</option>';
endforeach;
?>
</select>

请建议如何缩短javascript。可能代码的其他部分可以改进

---

澄清。默认值是

$options\u month

，

$options\u quarty

，

$options\u halfyear

中的第一个值（

[0]

）。首次加载页面时，可以看到

选择月份

，

选择季度

，

选择半年

。所以页面加载。用户从月份下拉菜单中选择例如<代码>二月。然后用户决定选择季度而不是月份。用户从quarters下拉菜单中选择第一个

。月份值下拉菜单自动更改为

选择月份

这是我的解决方案。简单得多。然而，我也改变了html布局

HTML更新：（在选择标记中有onchange）

...
...
...

Javascript更新：（减少到9行）

var dd_数组=['month_id'，'quarty_id'，'halfyear_id']；
功能更新\u其他\u dd（dd\u id）{
对于（i=0；i）您的问题特定于月份/季度、半年？当您说要更改默认值时，您的意思是要将其选中吗？您需要澄清您的问题。您是否尝试根据所选月份（依此类推）选择季度和半年，或者当选择一个月时，您是否试图将季度和半年更改为默认值？它们是非常不同的事情。我在问题的末尾写了澄清。
var month_for_update = document.getElementById( 'month_id' );
function updateQuarterHalfyear ( e ) {

var quarter = this.options[ this.selectedIndex ].value, quarterDDL= document.getElementById( 'quarter_id' ), quarter, i = quarterDDL.options.length - 1;

var halfyear = this.options[ this.selectedIndex ].value, halfyearDDL= document.getElementById( 'halfyear_id' ), halfyear, i = halfyearDDL.options.length - 1;

quarter = 0;
halfyear = 0;

for ( ; i > -1 ; i-- ) {
if ( quarterDDL.options[i].value == quarter ) {
quarterDDL.options[i].selected = true;
break;
}
}

for ( ; i > -1 ; i-- ) {
if ( halfyearDDL.options[i].value == halfyear ) {
halfyearDDL.options[i].selected = true;
break;
}
}

}

month_for_update.onchange = updateQuarterHalfyear;

/**/
var quarter_for_update = document.getElementById( 'quarter_id' );
function updateMonthHalfyear ( e ) {

var month = this.options[ this.selectedIndex ].value, monthDDL= document.getElementById( 'month_id' ), month, i = monthDDL.options.length - 1;

var halfyear = this.options[ this.selectedIndex ].value, halfyearDDL= document.getElementById( 'halfyear_id' ), halfyear, i = halfyearDDL.options.length - 1;

month = 0;
halfyear = 0;

for ( ; i > -1 ; i-- ) {
if ( monthDDL.options[i].value == month ) {
monthDDL.options[i].selected = true;
break;
}
}

for ( ; i > -1 ; i-- ) {
if ( halfyearDDL.options[i].value == halfyear ) {
halfyearDDL.options[i].selected = true;
break;
}
}

}

quarter_for_update.onchange = updateMonthHalfyear;


/**/
var halfyear_for_update = document.getElementById( 'halfyear_id' );
function updateMonthQuarter ( e ) {

var month = this.options[ this.selectedIndex ].value, monthDDL= document.getElementById( 'month_id' ), month, i = monthDDL.options.length - 1;

var quarter = this.options[ this.selectedIndex ].value, quarterDDL= document.getElementById( 'quarter_id' ), quarter, i = quarterDDL.options.length - 1;

month = 0;
quarter = 0;

for ( ; i > -1 ; i-- ) {
if ( monthDDL.options[i].value == month ) {
monthDDL.options[i].selected = true;
break;
}
}

for ( ; i > -1 ; i-- ) {
if ( quarterDDL.options[i].value == quarter ) {
quarterDDL.options[i].selected = true;
break;
}
}

}

halfyear_for_update.onchange = updateMonthQuarter;    

<select id="month_id" name="monthid" onchange="update_other_dd ( 'month_id' )">
...
<select id="quarter_id" name="quarterid" onchange="update_other_dd ( 'quarter_id' )">
...
<select id="halfyear_id" name="halfyearid" onchange="update_other_dd ( 'halfyear_id' )">
...

    var dd_array = ['month_id', 'quarter_id', 'halfyear_id'];
    function update_other_dd ( dd_id ) {
    for(i=0;i<dd_array.length;i++){
    if(dd_array[i] != dd_id){
        var array_to_reset = document.getElementById( dd_array[i] );
        array_to_reset.options[0].selected = 1;
    }
    }
    }