Question

如何检查下面的下拉列表中没有值？＆LT; TD＆GT; 选择角色＆LT; / TD＆GT; ＆LT; TD＆GT; ＆lt; select name =“RArole”id =“RArole”required＆gt; ＆lt; option value =“”＆gt;选择＆lt; / option＆gt; ＆lt; option value =“admin”＆gt; Admin＆lt; / option＆gt; ＆LT; /选择＆GT; ＆LT; / TD＆GT;

Answer 1

＆＃13;

function getValue() {
  var e = document.getElementById("RArole");
  var val = e.options[e.selectedIndex].value;
  alert(val.length);
}

＆＃13;

<select name="RArole" id="RArole" required onchange="getValue()">
  <option value="">Select</option>
  <option value="admin">Admin</option>
</select>

＆＃13;

Answer 2

<!DOCTYPE html>
<html>
<script data-require="jquery@*" data-semver="2.1.4" src="https://code.jquery.com/jquery-2.1.4.js"></script>

<script>
$(function(){
$("#RArole").on("change",function(){
var option = $("select").val();
if(option  === ""){
alert("No value");
}
});
});
</script>
<body>
<select name="RArole" id="RArole" required >
  <option value="">Select</option>
  <option value="admin">Admin</option>
</select>
</body>
</html>

使用javascript验证<select>元素

2 个答案: