[Beginning Rails 6] Listing 9-4. The Updated New Comment Template in app/views/comments/new.js.erb

new.js.erb

document.querySelector("#comments").insertAdjacentHTML("afterend", "<%= escape_javascript render partial: 'new' %>");

var comment_form = document.querySelector("#main form");
comment_form.style.opacity = 0;
setTimeout(function() {
  comment_form.style.transition = 'opacity 1s';
  comment_form.style.opacity = 1;
}, 10);

document.querySelector("#new_comment_link").style.display = 'none';