Javascript验证表单onsubmit未返回false

Question

注意：我搜索了类似的问题，但仍然无法解决，所以我再次询问。我有一个形式及其CCD_ 1。它检查文本区域是否为空。如果是，则返回false，但这不起作用。即使文本区域为空，操作仍然会转到下一个网站。

let firstName = document.querySelector('#firstname');
let lastName = document.querySelector('#lastname');
let password = document.querySelector('#password');
let retypePass = document.querySelector('#repassword');
let radioMale = document.querySelector('#male');
let radioFemale = document.querySelector('#female');
let textArea = document.querySelector('#textarea');
let select= document.querySelector('#select');
let button = document.querySelector('#button');
let form = document.querySelector('#form');
function submit(){
if (textArea.value = "") {
textArea.nextElementSibling.innerHTML = "Fill this box";
return false;
}
}
HTML :`

<div class='wrapper'>
<h1>Registration Form</h1>
<form  action="http://google.com" id='form' onsubmit="return submit()">
<input placeholder="First Name" type="text" id='firstname' required>
<span></span>
<br>
<input placeholder="Last Name" type="text" id='lastname' required>
<span></span>
<br>
<input placeholder="Password" type="text" id='password' required>
<span></span>
<br>
<input placeholder="Retype Password" type="text" id='repassword' required>
<span></span>
<br>
<input placeholder="Phone Number" type="tel" id='tel' >
<br>
<div class='radio'>
<h4>Selector Your Gender</h4>
<input type='radio'name='same' id='male'>Male
<input type='radio'name='same' id='female'>Female
</div>
<p style="margin:5px 0px;color:white">ADDRESS:</p>
<textarea id='textarea'></textarea>
<span></span>
<p style="margin:5px 0px;color:white">Country:</p>
<select type='country' style="width:84%" id='select'>
<option>England</option>
<option>Japan</option>
<option>America</option>
<option>France</option>
<option>NetherLands</option>
</select>
<br><br>
<input type='submit' value='submit'>
</form>
</div>

Answer 1

如果systax错误：

if (textArea.value = "")

应该是：

if (textArea.value == "")

Answer 2

您必须更改函数的名称

示例

<form action="http://google.com" id='form' onsubmit="return validate()">

和

function validate() {
if (textArea.value == "") {
textArea.nextElementSibling.innerHTML = "Fill this box";
return false;
}
}

Answer 3

尝试

if (!textArea.value) {
textArea.nextElementSibling.innerHTML = "Fill this box";
return false;
}

或

if (textArea.value == '') {
textArea.nextElementSibling.innerHTML = "Fill this box";
return false;
}