Expose todos_per_page variable

app/assets/javascripts/todos.js.coffee

 class @Todos
-  PER_PAGE = 20
-
   constructor: (@name) ->
+    @todos_per_page = gon.todos_per_page || 20
     @clearListeners()
     @initBtnListeners()
@@ -70,7 +69,7 @@ class @Todos
     currPages = @getRenderedPages()
     currPage = @getCurrentPage()
-    newPages = Math.ceil(total / PER_PAGE)
+    newPages = Math.ceil(total / @todos_per_page)
     url = location.href # Includes query strings
     # Refresh if no remaining Todos

app/controllers/dashboard/todos_controller.rb

@@ -2,6 +2,7 @@ class Dashboard::TodosController < Dashboard::ApplicationController
   before_action :find_todos, only: [:index, :destroy, :destroy_all]
   def index
+    gon.todos_per_page = Todo.default_per_page
     @todos = @todos.page(params[:page])
   end