javascript - 为什么我的 Javascript 验证不起作用？

Question

<script type='text/javascript'>
function formValidator(){
// Make quick references to our fields
var username = document.getElementByName('username');
var password = document.getElementByName('password');
var email = document.getElementByName('email');

// Check each input in the order that it appears in the form!
    if(isAlphanumeric(username, "Please only use letters and numbers for you username.")){
        if(lengthRestriction(username, 8, 12)){
            if(lengthRestriction(password, 6, 15)){
                if(emailValidator(email, "Please enter a valid email address")){
                            return true;
                }
            }
        }
    }


return false;
}


function isAlphanumeric(elem, helperMsg){
var alphaExp = /^[0-9a-zA-Z]+$/;
if(elem.value.match(alphaExp)){
    return true;
}else{
    alert(helperMsg);
    elem.focus();
    return false;
}
}

function lengthRestriction(elem, min, max){
var uInput = elem.value;
if(uInput.length >= min && uInput.length <= max){
    return true;
}else{
    alert("Please enter between " +min+ " and " +max+ " characters");
    elem.focus();
    return false;
}
}

function emailValidator(elem, helperMsg){
var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
if(elem.value.match(emailExp)){
    return true;
}else{
    alert(helperMsg);
    elem.focus();
    return false;
}
}

我的脚本不工作，即使用户名、密码和电子邮件文本框已经定义了名称属性。谢谢 :)。

Answer 1

getElementByName不是 document 的有效方法目的。你要getElement<em><b>s</b></em>ByName , 它将返回具有指定 name 的元素集合属性，或 getElementById()这将返回具有指定 id 的单个元素属性。

// get the first element with name="username"
var username = document.getElementsByName('username')[0];

// get the first element with name="password"
var password = document.getElementsByName('password')[0];

// get the first element with name="email"
var email = document.getElementsByName('email')[0];