我的所有 var 语句都使用标识符:
var identifier = document.getElementById("somename");
那么为什么我会收到空错误？ 我在 Javascript 运行程序中运行此代码并收到 null 错误消息。在我的浏览器 Firefox 和 Chrome 中，我没有收到任何错误或警告。当我在浏览器中运行代码并单击按钮激活事件处理程序时，表单将被清除。无论如何，它不会发送到服务器。这只是练习。我正在学习 javascript 和动态 HTML 类(class)。如果有人愿意查看我的代码并告诉我我做错了什么，我将不胜感激。 一定有什么地方我没搞对。这是脚本:
window.onload = function(){
var fname = document.getElementById("fname").value;
var lname = document.getElementById("lname").value;
var loginName = document.getElementById("uname").value;
var myEmail = document.getElementById("email").value;
var pass1 = document.getElementById("password1").value;
var pass2 = document.getElementById("password2").value;
if(document.getElementById("uname").value == ""){
return false;
alert("Your user name can't be blank.");
};
if(pass1.value !== pass2.value){
get.documentElementById("signin").value.disabled = true;
return false;
alert("Please retype your password.");
}else if(pass1.value === pass2.value){
alert("Welcome!");
};
};
HTML
<body>
<form action = "" name = "form" method = "Post">
<label for="fname">First Name:</label><input type = "text" id = "fname"required></input>
<label for="lname">Last Name:</label><input type = "text" id = "lname" required></input>
<label for="uname">User Name:</label><input type = "text" id = "uname" required></input><br/>
<label for="password1">Password:</label><input type = "password" id = "password1"required ></input><br/>
<label for="password2">Verify Password:</label><input type = "password" id = "password2"required ></input><br/>
<label for="email">Email Address:</label><input type = "email" id = "email" required></input><br/>
<button type = "submit"id = "signin" onclick = "function()">Submit</button>
</form>
<script src="signUp.js"></script>
</body>
最佳答案
我为你清理了你的代码。有几个地方出现错误(例如，输入 pass1.value 而不是仅 pass1。这应该可行，但当然需要时间研究它以了解我的情况更改并理解原因。Here's a fiddle showing it working. 请注意，您永远不应该期望此类代码在您引用的“运行者”中运行；此处的代码显式引用 DOM 中的特定元素，运行者赢得了这些元素没有。(使用像 JSFiddle 这样的网站更适合此类事情，因为您也可以将 HTML 放入其中)。
var submitForm = function () {
var fname = document.getElementById("fname").value;
var lname = document.getElementById("lname").value;
var loginName = document.getElementById("uname").value;
var myEmail = document.getElementById("email").value;
var pass1 = document.getElementById("password1").value;
var pass2 = document.getElementById("password2").value;
console.log(pass1, pass2);
if (document.getElementById("uname").value == "") {
alert("Your user name can't be blank.");
return false;
}
if (pass1 !== pass2) {
document.getElementById("signin").value.disabled = true;
alert("Please retype your password.");
return false;
} else if (pass1 === pass2) {
alert("Welcome!");
}
};
<body>
<form action="" name="form" method="POST">
<label for="fname">First Name:</label><input type ="text" id = "fname" required></input>
<label for="lname">Last Name:</label><input type = "text" id = "lname" required></input>
<label for="uname">User Name:</label><input type ="text" id ="uname" required></input><br/>
<label for="password1">Password:</label><input type="password" id="password1" required></input><br/>
<label for="password2">Verify Password:</label><input type="password" id="password2" required ></input><br/>
<label for="email">Email Address:</label><input type="email" id="email" required></input><br/>
<button type="submit" id="signin" onclick="submitForm()">Submit</button>
</form>
</body>
关于javascript - 类型错误 : document. getElementById(...);在 JavaScript 中为 null，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33795400/