Javascript <；选择>；验证无效

嘿，伙计们，我想用javascript进行验证，我尝试了互联网上的每一种方法——它不起作用，它会清除每个字段并刷新页面。 我需要的是证实他选择了他的国籍

这是我的javascript代码

function signin(){
                var a=document.forms["signin"]["inemail"].value;
                if(a==null || a==""){
                alert("Please enter an Email!!");
                document.getElementById("upemail").innerHTML="<font color=red>email is empty</font>"
                return false;
        }
            }
        function signUp(){
        var x1 = document.forms["signup"]["upemail"].value;
        var x2 = document.forms["signup"]["uppassword"].value;
        var x3 = document.forms["signup"]["repassword"].value;
        var x4 = document.forms["signup"]["fname"].value;
        var x5 = document.forms["signup"]["lname"].value;
        var x6 = document.forms["signup"]["dob"].value;
        var x7 = document.forms["signup"]["gender"].value;
        var x8 = document.forms["signup"]["nationality"].value;
        var atpos=x1.indexOf("@");
        var dotpos=x1.lastIndexOf(".");
        var date = document.getElementById('dob').value;
        var minLength = 6;
        var nationality = document.getElementByName("nationality")[0].value;


        if(x1==null || x1==""){
        alert("Please enter an Email!!");
        document.getElementById("upemail").innerHTML="<font color=red>email is empty</font>"
        return false;
        }
        else if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)
        {
        alert("Not a valid e-mail address");
        return false;
        }
        else if(x2==null || x2==""){
        alert("Please enter a password!!");
        return false;
        }
        else if(x3==null || x3==""){
        alert("Please re-enter your password");
        return false;
        }
        else if(document.signup.uppassword.value.length < minLength){
        alert("Password must be minimum 6 character");  
        }
        else if(x3 != x2){
        alert("password does not match");   
        }
        else if(x4==null || x4==""){
        alert("Please enter your first name");
        return false;
        }
        else if(x5==null || x5==""){
        alert("Please enter your last name");
        return false;
        }
        else if(x6==null || x6==""){
        alert("Please enter your Date of Birth");
        return false;
        }
        else if ( form.gender[0].checked == false  &&  form.gender[1].checked == false ) { 
        alert ( "Please choose your Gender: Male or Female" ); return false; 
        }
        else if (date == "" ||date == null ){ 
        alert("Date of Birth must be chosen"); 
        return false; 
        }
        else if(nationality == "none"){
        alert("Please enter your nationality")  
        }
        else{
        alert("sucssefully")
        return true;
        }


    }

这就是表单的标题

<form name ="signup" action="" onsubmit="return signUp()" method="post">

这是我选择标签的一部分

<select name="nationality" class="input" id="nationality">
                            <option value="none" selected>Country...</option>
                            <option value="Afganistan">Afghanistan</option>
                            <option value="Albania">Albania</option>
                            <option value="Algeria">Algeria</option>
                            <option value="American Samoa">American Samoa</option>

国家。。。
阿富汗
阿尔巴尼亚
阿尔及利亚
美属萨摩亚

请再试一次

if(document.getElementById('nationality').selectedIndex == 0)
{
alert("Please select Nationality");
return false;
}

或

---

没有函数

document.getElementByName

，它是

document.getElementsByName

复数形式

改为

var nationality = document.getElementsByName("nationality")[0].value;

---

如果您查看控制台，您将看到一个错误，指出这一点。

您可以使用

selectedIndex

属性，该属性检查selectbox的选定索引

var elem = document.getElementById("nationality");
if(elem.selectedIndex == 0)
{
     alert("You must choose");   
}
else
{
    alert("You have chosen wisely");
}

它们使用

返回false

，就像您对其他字段所做的那样

---

请查看此提琴以获取完整代码-

在JavaScript控制台上查看提琴将非常有用-

TypeError:Object#没有方法“getElementByName”

JavaScript控制台中显示了什么错误

var nationality = document.getElementsByName("nationality")[0].value;

var elem = document.getElementById("nationality");
if(elem.selectedIndex == 0)
{
     alert("You must choose");   
}
else
{
    alert("You have chosen wisely");
}