Passing nested parameters to an ajax get request - ruby-on-rails

Question

In a Rails 5.1 app (without jQuery) how can I pass nested params via a GET ajax request?
I have the following
Rails.ajax({
url: select.getAttribute('data-url') + "?xxx",
type: "GET"
});
If I replace xxx with, for instance, pippo=pluto, in my controller
params[:name] #=> "pluto"
However, in my controller, I need to be able to access a nested param as below.
params[:user][:name] #=> "pluto"
It seems a simple problem but I cannot find a solution.
Here my JS
document.addEventListener('turbolinks:load', function() {
var select = document.querySelector("select[name='user[name]']")
if(select.options[select.selectedIndex].value) {
Rails.ajax({
url: select.getAttribute('data-url'),
type: "GET",
data: {
user: {
name: select.options[select.selectedIndex].value
}
}
});
}
});
Which produces (user[:name] is always selected)
{"object Object"=>nil, "controller"=>"steps", "action"=>"index"} permitted: false>
The query string works fine (but is ugly)
Rails.ajax({
url: select.getAttribute('data-url') + '?user[name]=' + select.options[select.selectedIndex].value,
type: "GET"
});
SIDE QUESTION: To avoid the ajax request in the first place is there an alternative way to automatically trigger the request of the select below when the page is loaded? Currently, it is triggered only when the selected option changes
<%= f.select :user, MyUsers.all,
{ data: { remote: true, url: duplicate_users_path } } %>

Answer 1

use data option in ajax (recommended)
Rails.ajax({
url: select.getAttribute('data-url'),
type: 'GET',
data: {
users: {
pippo: 'pluto',
pippo2: 'pluto2'
}
}
});
or query string as array
Rails.ajax({
url: select.getAttribute('data-url') + '?users[pippo]=pluto&users[pippo2]=pluto2',
type: 'GET'
});