How to add data before submitting ActiveForm on client?

Question

Yii

Good afternoon, I'm sure the noob question is just awful, but I'm a little confused and don't understand how to do it.
In general, there is activeForm, and there is content that the user creates, js is generated.
This data is not form fields, it's just json objects, but I need to pass it along with the form on submit.
How to do it so as not to abandon activeForm ?

Answer 1

1) event beforeSubmit
2) as the js event occurs, immediately write to the hidden field in the form.