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,应该在下拉列表2和3中禁用该项目.此外,如果在下拉列表2中选择了某个项目,则必须从下拉列表3中禁用所有选定项目.
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> …