TypeError:无法读取null的属性"classList" [英] TypeError: Cannot read property 'classList' of null
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问题描述
我遇到错误
TypeError: Cannot read property 'classList' of null
我不确定在操作每个表单字段的DOM元素时我做错了什么.我的表单字段具有表单的声明名称和ID，每个输入字段也具有该字段的名称和ID.但是我仍然遇到错误.
I am not really sure what am I doing wrong in manipulating DOM element for each form field. My form field has an stated name and ID of form and each input field has a name and id of the field as well. But I am still getting an error.
我在做什么错了?
我的脚本:
document.querySelector("#form").addEventListener("submit", function(e){
//create variable for contact form url
var formURL = 'melonForm.php';
//prevent default submission
event.preventDefault();
//define form fields
var melonForm = {
'firstName' : document.querySelector('input[name=firstName]').value,
'lastName' : document.querySelector('input[name=lastName]').value,
'companyName' : document.querySelector('input[name=companyName]').value,
'companyAddress' : document.querySelector('input[name=companyAddress]').value,
'city' : document.querySelector('input[name=city]').value,
'state' : document.querySelector('select[name=state]').value,
'zipcode' : document.querySelector('input[name=zipcode]').value,
'emailAddress' : document.querySelector('input[name=emailAddress]').value,
'phoneNumber' : document.querySelector('input[name=phoneNumber]').value,
}
//define request variable
var formRequest = new Request(formURL, {
method: 'POST',
body: melonForm,
headers: new Headers()
});
//fetch
fetch(formRequest)
.then(function(formResponse) {
return formResponse.json();
})
.then(function(data) {
//handle server responses
if ( ! data.success) {
//handle error messages
//handle error message for firstName
console.log(data);
if (data.errors.firstName) {
document.getElementById("firstName").classList.add("has-error");
document.getElementById("firstName").appendChild('<div class="help-block">' + data.errors.firstName + '</div>');
}
//handle errors for lastName
if (data.errors.lastName) {
document.getElementById("lastName").classList.add("has-error");
document.getElementById("lastName").appendChild('<div class="help-block">' + data.errors.lastName + '</div>');
}
//handle errors for companyName
if (data.errors.companyName) {
document.getElementById("companyName").classList.add("has-error");
document.getElementById("companyName").appendChild('<div class="help-block">' + data.errors.companyName + '</div>');
}
//handle errors for companyAddress
if (data.errors.companyAddress) {
document.getElementById("companyAddress").classList.add("has-error");
document.getElementById("companyAddress").appendChild('<div class="help-block">' + data.errors.companyAddress + '</div>');
}
//handle errors for city
if (data.errors.city) {
document.getElementById("city").classList.add("has-error");
document.getElementById("city").appendChild('<div class="help-block">' + data.errors.city + '</div>');
}
//handle errors for state
if (data.errors.state) {
document.getElementById("state").classList.add("has-error");
document.getElementById("statea").appendChild('<div class="help-block">' + data.errors.state + '</div>');
}
//handle errors for zipcode
if (data.errors.zipcode) {
document.getElementById("zipcode").classList.add("has-error");
document.getElementById("zipcode").appendChild('<div class="help-block">' + data.errors.zipcode + '</div>');
}
//handle errors for emailAddress
if (data.errors.emailAddress) {
document.getElementById("emailAddress").classList.add("has-error");
document.getElementById("emailAddress").appendChild('<div class="help-block">' + data.errors.emailAddress + '</div>');
}
//handle errors for phoneNumber
if (data.errors.phoneNumber) {
document.getElementById("phoneNumber").classList.add("has-error");
document.getElementById("phoneNumber").appendChild('<div class="help-block">' + data.errors.phoneNumber + '</div>');
}
// handle errors for captcha ---------------
if (data.errors.captcha) {
swal({
title: "Error!",
text: data.errors.captcha,
icon: "error",
});
}
// handle errors for phpmailer ---------------
if (data.message) {
swal({
title: "Error!",
text: data.message,
icon: "error",
});
}
else {
//handle success messages
swal({
title: "Success!",
text: data.message,
icon: "success",
});
document.getElementById("form").reset();
}
}
});
})
我知道html中确实存在firstName字段，但不确定为什么javascript无法读取该元素.
I know that the field firstName does exist in the html but not sure why the javascript is not able to read the element.
添加了HTML:
<html>
<head>
<title>Melon Form</title>
<link rel="stylesheet" href="https://netdna.bootstrapcdn.com/bootstrap/3.0.3/css/bootstrap.min.css"> <!-- load bootstrap via CDN -->
<script src="https://unpkg.com/sweetalert/dist/sweetalert.min.js"></script>
</head>
<body>
<div class="col-sm-6 col-sm-offset-3">
<h1>Contact Form</h1>
<!-- OUR FORM -->
<form name="form" id="form" action="melonForm.php" method="POST">
<!-- FIRST NAME -->
<div id="firstName-group" class="form-group">
<label for="firstName">First Name:</label>
<input type="text" class="form-control" name="firstName" placeholder="Henry Pym">
<!-- errors will go here -->
</div>
<!-- LAST NAME -->
<div id="lastName-group" class="form-group">
<label for="lastName">Last Name:</label>
<input type="text" class="form-control" name="lastName" placeholder="Henry Pym">
<!-- errors will go here -->
</div>
<!-- COMPANY NAME -->
<div id="companyName-group" class="form-group">
<label for="companyName">Company Name:</label>
<input type="text" class="form-control" name="companyName" placeholder="Henry Pym">
<!-- errors will go here -->
</div>
<!-- COMPANY ADDRESS -->
<div id="companyAddress-group" class="form-group">
<label for="companyAddress">Company Address:</label>
<input type="text" class="form-control" name="companyAddress" placeholder="Henry Pym">
<!-- errors will go here -->
</div>
<!-- CITY -->
<div id="city-group" class="form-group">
<label for="city">City:</label>
<input type="text" class="form-control" name="city" id="city" placeholder="Henry Pym">
<!-- errors will go here -->
</div>
<div id="state-group" class="form-group">
<label for="state">State</label>
<select id="state" name="state" class="form-control">
<option value="" selected>Choose...</option>
<option value="AL">Alabama</option>
<option value="AK">Alaska</option>
<option value="AZ">Arizona</option>
<option value="AR">Arkansas</option>
<option value="CA">California</option>
<option value="CO">Colorado</option>
<option value="CT">Connecticut</option>
<option value="DE">Delaware</option>
<option value="DC">District Of Columbia</option>
<option value="FL">Florida</option>
<option value="GA">Georgia</option>
<option value="HI">Hawaii</option>
<option value="ID">Idaho</option>
<option value="IL">Illinois</option>
<option value="IN">Indiana</option>
<option value="IA">Iowa</option>
<option value="KS">Kansas</option>
<option value="KY">Kentucky</option>
<option value="LA">Louisiana</option>
<option value="ME">Maine</option>
<option value="MD">Maryland</option>
<option value="MA">Massachusetts</option>
<option value="MI">Michigan</option>
<option value="MN">Minnesota</option>
<option value="MS">Mississippi</option>
<option value="MO">Missouri</option>
<option value="MT">Montana</option>
<option value="NE">Nebraska</option>
<option value="NV">Nevada</option>
<option value="NH">New Hampshire</option>
<option value="NJ">New Jersey</option>
<option value="NM">New Mexico</option>
<option value="NY">New York</option>
<option value="NC">North Carolina</option>
<option value="ND">North Dakota</option>
<option value="OH">Ohio</option>
<option value="OK">Oklahoma</option>
<option value="OR">Oregon</option>
<option value="PA">Pennsylvania</option>
<option value="RI">Rhode Island</option>
<option value="SC">South Carolina</option>
<option value="SD">South Dakota</option>
<option value="TN">Tennessee</option>
<option value="TX">Texas</option>
<option value="UT">Utah</option>
<option value="VT">Vermont</option>
<option value="VA">Virginia</option>
<option value="WA">Washington</option>
<option value="WV">West Virginia</option>
<option value="WI">Wisconsin</option>
<option value="WY">Wyoming</option>
</select>
</div>
<!-- ZIPCODE -->
<div id="zipcode-group" class="form-group">
<label for="zipcode">Zipcode:</label>
<input type="text" class="form-control" name="zipcode" id="zipcode" placeholder="12345">
<!-- errors will go here -->
</div>
<!-- EMAIL ADDRESS -->
<div id="emailAddress-group" class="form-group">
<label for="emailAddress">Email Address:</label>
<input type="text" class="form-control" name="emailAddress" placeholder="rudd@avengers.com">
<!-- errors will go here -->
</div>
<!-- PHONE NUMBER -->
<div id="phoneNumber-group" class="form-group">
<label for="phoneNumber">Phone Number:</label>
<input type="text" class="form-control" name="phoneNumber" id="phoneNumber" placeholder="12345">
<!-- errors will go here -->
</div>
<!-- MESSAGE -->
<div id="message-group" class="form-group">
<label for="message">Message:</label>
<input type="text" class="form-control" name="message" placeholder="Ant Man">
<!-- errors will go here -->
</div>
<!-- GOOGLE RECAPTCHA -->
<div class="form-group">
<div class="g-recaptcha" data-sitekey="SECRET_KEY"></div>
</div>
<button type="submit" class="btn btn-success">Submit <span class="fa fa-arrow-right"></span></button>
</form>
</div>
<script src="melonForm.js" defer></script> <!-- load our javascript file -->
</body>
<script src='https://www.google.com/recaptcha/api.js'></script>
</html>
推荐答案
这意味着 document.getElementById("lastName")返回 undefined ，而您正在尝试在 undefined 本身上调用 classList .
It means that document.getElementById("lastName") is returning undefined and you're trying to call classList on undefined itself.
在您的HTML input 中具有属性 name ，该属性等于 lastName ，但是没有实际的 id ="lastname"
In your HTML input has the attribute name which equals lastName but there is no actual id="lastname"
将属性 id 添加到 input 或将 getElementById 更改为 getElementsByName .
Either add the attribute id to your input or change getElementById to getElementsByName.
请注意， getElementsByName 不会返回单个项目.
Note that getElementsByName doesn't return a single item.
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