How do you send an ajax request every time that a form input field changes?

Question

For example, there is an input field. Every time a user types a key into that field, it sends an AJAX request with whatever text is currently in that input, and does something

Answer 1

I'd probably do something similar to this. you'd have to add some extra code to handle dropdowns, but the idea is the same.

$('form input').keyup(function () {
    $.ajax({
      type: "POST",
      url: url,
      data: data,
      success: success,
      dataType: dataType
    });
});