我有一个网页,其中 2 个在标题中,2 个在主页正文中使用 4 个搜索框。 标题形式和首页正文形式相同,查询相同的搜索页面。
我的问题是如何链接下拉菜单,以便当一个下拉菜单发生更改时,其他下拉菜单也会跟随。
目前,我正在使用 php 在到达页面时切换到适当的类别。
例如:
<option value='-1' <?php if ($cat == "-1") {print("selected");}?>>All Categories</option>
<option value='0'<?php if ($cat == "0") {print("selected");}?>>Category One</option>
<option value='1' <?php if ($cat == "1") {print("selected");}?>>Category Two</option>
在查询后到达页面时效果很好。
但是,因为我的主页上有 4 个表单,所以当用户更改页面上的 < select >< options > 之一时,我希望以某种方式动态地更改标题和其他位置中的其他 < select >< options > 全部更改为也有同样的值(value)吗?
有什么想法吗?
最佳答案
假设您有 2 个“选择”html 元素,如下所示:
测试.html
<html>
<head>
<script src="connectSelect.js"></script>
</head>
<body onload="connectSelect('first', 'second')">
<select id="first">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<select id="second">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
</body>
</html>
只需在主体负载上使用已创建的“connectSelect”函数,传递要连接的“Select”元素的 ID。
在 header 中包含 connectSelect.js 文件。下面是代码:
connectSelect.js
function connectSelect(id1, id2) {
var select1 = document.getElementById(id1);
var select2 = document.getElementById(id2);
var i, val1, text1, val2, text2, errText;
//to check whether both the select elements are of same length or not
if (select1.length != select2.length) {
alert("connectSelect Function Error: Both the 'Select' elements should have same number of options!");
return;
}
//after assuring both the select elements to be of same length
//to check whether both the select elements have same value and text
for (i = 0; i < select1.length; i++) {
val1 = select1.options[i].value;
text1 = select1.options[i].innerHTML;
val2 = select2.options[i].value;
text2 = select2.options[i].innerHTML;
if (val1 != val2 || text1 != text2) {
errText = "Both the 'Select' elements should have same options with same value and text!";
errText += "\n";
errText += "\n";
errText += "First mismatch: Option " + (i+1);
alert("connectSelect Function Error: " + errText);
return;
}
}
//after assuring both the select elements to be same
select1.addEventListener("change", function(){
var index = this.selectedIndex;
select2.options[index].selected = true;
});
select2.addEventListener("change", function(){
var index = this.selectedIndex;
select1.options[index].selected = true;
});
}
我也插入了代码片段。尝试一下。
function connectSelect(id1, id2) {
var select1 = document.getElementById(id1);
var select2 = document.getElementById(id2);
var i, val1, text1, val2, text2, errText;
//to check whether both the select elements are of same length or not
if (select1.length != select2.length) {
alert("connectSelect Function Error: Both the 'Select' elements should have same number of options!");
return;
}
//after assuring both the select elements to be of same length
//to check whether both the select elements have same value and text
for (i = 0; i < select1.length; i++) {
val1 = select1.options[i].value;
text1 = select1.options[i].innerHTML;
val2 = select2.options[i].value;
text2 = select2.options[i].innerHTML;
if (val1 != val2 || text1 != text2) {
errText = "Both the 'Select' elements should have same options with same value and text!";
errText += "\n";
errText += "\n";
errText += "First mismatch: Option " + (i+1);
alert("connectSelect Function Error: " + errText);
return;
}
}
//after assuring both the select elements to be same
select1.addEventListener("change", function(){
var index = this.selectedIndex;
select2.options[index].selected = true;
});
select2.addEventListener("change", function(){
var index = this.selectedIndex;
select1.options[index].selected = true;
});
}
<html>
<head>
<script src="test.js"></script>
</head>
<body onload="connectSelect('first', 'second')">
<select id="first">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<select id="second">
<option value="0">0</option>
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
</body>
</html>
希望有帮助。
编辑:为了更好的解决方案,请检查 this (来源:来自该问题的评论)
关于javascript - 如何链接到表单选择选项下拉列表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43632008/