我有三个下拉菜单。我希望当用户从下拉列表 1 中选择任何项目时,应在下拉列表 2 和 3 中禁用该项目。此外,如果在下拉列表 2 中选择了一个项目,则必须从下拉列表 3 中禁用两个选定项目。
这是我正在使用的代码:
<!DOCTYPE html>
<html>
<head>
<script>
function updateSelect(changedSelect, selectId) {
var otherSelect = document.getElementById(selectId);
for (var i = 0; i < otherSelect.options.length; ++i) {
otherSelect.options[i].disabled = false;
}
if (changedSelect.selectedIndex == 0) {
return;
}
otherSelect.options[changedSelect.selectedIndex].disabled = true;
}
</script>
</head>
<body>
<select id="select_1" onchange="updateSelect(this,'select_2'),updateSelect(this,'select_3');" name="indication_subject[]">
<option value="" selected="selected">a </option>
<option value="1"> Accounting</option>
<option value="2"> Afrikaans</option>
<option value="3"> Applied Information and Communication Technology</option>
<option value="4"> Arabic</option>
<option value="5"> Art and Design</option>
<option value="6"> Biology</option>
<option value="7"> Business Studies</option>
</select>
<select id="select_2" name="indication_subject[]" onchange="updateSelect(this,'select_1','select_3');" >
<option value="" selected="selected">a </option>
<option value="1"> Accounting</option>
<option value="2"> Afrikaans</option>
<option value="3"> Applied Information and Communication Technology</option>
<option value="4"> Arabic</option>
<option value="5"> Art and Design</option>
<option value="6"> Biology</option>
<option value="7"> Business Studies</option>
</select>
<select id="select_3" name="indication_subject[]" onchange="updateSelect(this,'select_1','select_2');" >
<option value="" selected="selected">a </option>
<option value="1"> Accounting</option>
<option value="2"> Afrikaans</option>
<option value="3"> Applied Information and Communication Technology</option>
<option value="4"> Arabic</option>
<option value="5"> Art and Design</option>
<option value="6"> Biology</option>
<option value="7"> Business Studies</option>
</select>
</body>
</html>
下面是适用于两个下拉菜单的 JSFiddle 链接,而不是三个。如何为此添加第三个下拉列表?