Make js init play nice with turbolinks

app/assets/javascripts/vanilla_nested.js

@@ -127,13 +127,24 @@
     return undo;
   }
 
-  document.addEventListener('DOMContentLoaded', function(){
+  function initVanillaNested() {
     document.querySelectorAll('.vanilla-nested-add').forEach(el => {
       el.addEventListener('click', addVanillaNestedFields, true);
     })
 
     document.querySelectorAll('.vanilla-nested-remove').forEach(el => {
       el.addEventListener('click', removeVanillaNestedFields, true);
     })
+  }
+
+  document.addEventListener('DOMContentLoaded', function(){
+    initVanillaNested();
+  })
+
+  // Don't run turbolinks event callback for first load, we already do it with DOMContentLoaded
+  const notEmpty = (obj) => Object.keys(obj).length;
+
+  document.addEventListener('turbolinks:load', function(e){
+    if (notEmpty(e.data.timing)) initVanillaNested();
   })
 })()

test/VanillaNestedTests/app/views/users/index.html.erb

@@ -0,0 +1 @@
+<%= link_to 'New User', new_user_path %>

test/VanillaNestedTests/app/views/users/new.html.erb

@@ -1 +1,2 @@
-<%= render partial: 'form', locals: {user: @user} %>
+<%= render partial: 'form', locals: {user: @user} %>
+<%= link_to 'Back', users_path %>

test/VanillaNestedTests/test/system/vanilla_nested_test.rb

@@ -2,7 +2,8 @@
 
 class VanillaNestedTest < ApplicationSystemTestCase
   test "adds/removes fields" do
-    visit new_user_path
+    visit users_path
+    click_link 'New User'
 
     assert_selector '#new_user'