jQuery Form Plugin Ignored when submitting form - html

Question

I created an html form which submits data to my backend when submitted. The backend then redirects the webpage and shows a json message. I would like to remain on the same page and capture that json message to show to the user. I tried doing this using AJAX forms (https://jquery-form.github.io/form/) however upon clicking the submit button, the page still redirects and the script is kind of ignored.
Script included in the head after the CSS:
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery.form/4.2.2/jquery.form.min.js" integrity="sha384-FzT3vTVGXqf7wRfy8k4BiyzvbNfeYjK+frTVqZeNDFl8woCbF0CYG6g2fMEFFo/i" crossorigin="anonymous"></script>
<script src="https://code.jquery.com/jquery-3.4.1.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
<script>
// wait for the DOM to be loaded
$(function() {
// bind 'myForm' and provide a simple callback function
$('#signup-form').ajaxForm(function() {
alert("Thank you for your comment!");
});
});
</script>
The form:
<form id="signup-form" action="https://example-placeholder.com/api/auth/register" method="POST">
<div class="form-group row">
<div class="col">
<input type="email" class="form-control" id="username" name="username" placeholder="Email" required>
</div>
</div>
<div class="form-group row">
<div class="col">
<input type="password" class="form-control" id="password" name="password" placeholder="Password" required>
</div>
</div>
<div class="form-group row">
<div class="col">
<button type="submit" class="btn btn-custom btn-block" id="register-button">Register</button>
</div>
</div>
<label id="submit-label" style="display: none;">Check your inbox to activate your account!</label>
</form>
Response returned by backend:
return response()->json([
'message' => 'Successfully created user!'
], 201);
Errors returned by Google Chrome:
UPDATE (To fix CORS Error):
Added the following three lines before RewriteEngine On in the .htaccess file of my backend:
Header add Access-Control-Allow-Origin "*"
Header add Access-Control-Allow-Headers "origin, x-requested-with, content-type"
Header add Access-Control-Allow-Methods "PUT, GET, POST, DELETE, OPTIONS"