standard function format ajax jquery

$.ajax({
method: "POST",
url: url,
data: data, 
contenType: Type,
success: function(){}, 
error: function(){} 
});

for example html form send data json:

<div class="col-3 ml-3">
<h4>Register</h4>
<form id="sigup">
<div class="mb-3">
<label for="exampleInputEmail1" class="form-label">Name</label>
<input type="email" class="form-control" name="name">
</div>
<div class="mb-3">
<label for="exampleInputEmail1" class="form-label">Username</label>
<input type="text" class="form-control" name="username">
<div id="emailHelp" class="form-text">We'll never share your username anyone!</div>
</div>
<div class="mb-3">
<label for="exampleInputPassword1" class="form-label">Password</label>
<input type="password" class="form-control" name="password">
</div>
<p id="msg"></p>
<button type="button" class="btn btn-primary">Sig Up</button>
</form>
</div>

This sending post from ajax jquery get data from :

<script type="text/javascript">

$(document).ready(function(){
$("#sigup").click(function(){

var data = document.getElementById('sigup');
var formData = new FormData(data);
console.log(JSON.stringify(Object.fromEntries(formData)));

$.ajax({
method: "POST",
url: "<?=base_url('user/register');?>",
data:JSON.stringify(Object.fromEntries(formData)),
contentType: "application/json",

success: function(res){ // respon db, if OK
if(res==1){
msg_('<font color=green> Add succesfully.</font>');
$('#sigup')[0].reset();
console.log(res);
}else{
msg_('<font color=red>'+res+'</font>');
console.log(res);
}
},

error: function(res){ // respon ajax, jquery before controller
console.log(res);
}
});// you have missed this bracket

});
});

</script>

Get more example, ajax jquery post + PHP : stack overflow.