File: C:/Redmine-4.x/redmine-4.2.9/app/views/issues/new.js.erb
replaceIssueFormWith('<%= escape_javascript(render :partial => 'form') %>');
<% case params[:form_update_triggered_by] %>
<% when "issue_project_id" %>
$("#watchers_form_container").html(
'<%= escape_javascript(render :partial => 'issues/watchers_form') %>');
<% when "issue_category_id" %>
$('#issue_assigned_to_id').find('option').first().html(
'<%= escape_javascript(
@issue.category.try(:assigned_to).try(:name)).presence || ' '.html_safe %>');
<% end %>