Blog Demo

A classic Rails blog with articles and comments. The same code runs on Rails, in browsers with IndexedDB, on Node.js with SQLite, and on edge platforms.

Table of Contents

Create the App

curl -sL https://raw.githubusercontent.com/ruby2js/ruby2js/master/test/blog/create-blog | bash -s blog
cd blog

This creates a Rails app with:

  • Article scaffold — title, body, CRUD operations
  • Comment scaffold — nested under articles, belongs_to :article
  • Associations — has_many :comments, dependent: :destroy
  • Validations — validates :title, presence: true, validates :body, length: { minimum: 10 }
  • Nested routes — resources :articles { resources :comments }
  • Tailwind CSS — styled forms and layouts
  • Sample data — seeded articles and comments

Run with Rails

First, verify it works as a standard Rails app:

RAILS_ENV=production bin/rails db:prepare
bin/rails server -e production

Open http://localhost:3000. Browse articles. Add comments. Delete them. This is Rails as you know it—CRuby, SQLite, the full stack.

Run in the Browser

Stop Rails. Run the same app in your browser:

bin/juntos dev -d dexie

Open http://localhost:3000. Same blog. Same articles. Same comments. But now:

  • No Ruby runtime — the browser runs transpiled JavaScript
  • IndexedDB storage — data persists in your browser via Dexie
  • Hot reload — edit a Ruby file, save, browser refreshes
  • Auto-migrations — database schema updates automatically on startup

Debugging in DevTools

Open DevTools. In the Sources panel, find your Ruby files—app/models/article.rb, app/controllers/articles_controller.rb. Set breakpoints on Ruby lines. Step through Ruby code. Inspect variables with Ruby names.

The Console shows Rails-style logging:

Article Create {title: "Hello", body: "World", created_at: "..."}
Article Update {id: 1, title: "Updated", updated_at: "..."}

Run on Node.js

bin/juntos db:prepare -d sqlite
bin/juntos up -d sqlite

Open http://localhost:3000. Same blog—but now Node.js serves requests, and better-sqlite3 provides the database.

The db:prepare command runs migrations and seeds if the database is fresh. The up command builds and starts the server.

Other runtimes work too:

bin/juntos up -t bun -d sqlite    # Bun runtime
bin/juntos up -t deno -d postgres  # Deno with PostgreSQL

Deploy to Vercel

bin/juntos db:prepare -d neon
bin/juntos deploy -d neon

Prerequisites:

  1. Vercel CLI — npm i -g vercel and vercel login
  2. Create a Vercel project — run vercel once to link
  3. Create a Neon database
  4. Connect database — add DATABASE_URL as a Vercel environment variable
  5. Local environment — copy credentials to .env.local for migrations

Like Rails, migrations run separately from deployment. The db:prepare command applies migrations and seeds if fresh. The deploy command builds and deploys.

Deploy to Cloudflare

bin/juntos db:prepare -d d1
bin/juntos deploy -d d1

Prerequisites:

  1. Wrangler CLI — npm i -g wrangler and wrangler login

The db:prepare command creates the D1 database (if not already set up), runs migrations, and seeds if fresh. The database ID is saved to .env.local automatically as D1_DATABASE_ID (for development) or D1_DATABASE_ID_PRODUCTION (for production).

The Code

The code is idiomatic Rails. Try it — edit the Ruby to see how models transpile:

class Article < ApplicationRecord
  has_many :comments, dependent: :destroy
  validates :title, presence: true
  validates :body, presence: true, length: { minimum: 10 }
end

Try it — controllers also transpile directly:

class ArticlesController < ApplicationController
  before_action :set_article, only: %i[show edit update destroy]

  def index
    @articles = Article.all
  end

  def show
  end

  def create
    @article = Article.new(article_params)
    if @article.save
      redirect_to @article
    else
      render :new, status: :unprocessable_entity
    end
  end

  private

  def set_article
    @article = Article.find(params[:id])
  end
end

Nothing special. Nothing modified for transpilation. Standard Rails conventions work.

What This Demo Shows

Model Layer

  • has_many and belongs_to associations
  • dependent: :destroy for cascading deletes
  • validates with presence and length

Controller Layer

  • before_action callbacks
  • Instance variable assignment (@article)
  • Standard CRUD actions
  • redirect_to and render
  • Strong parameters (article_params)

View Layer

  • ERB templates with <%= %> and <% %>
  • link_to, button_to, form_with
  • Nested forms for comments
  • Partials (_article.html.erb, _comment.html.erb)
  • Layouts with yield

Routes

  • resources :articles
  • Nested resources :comments
  • root "articles#index"
  • Generated path helpers (article_path, new_article_path)

What Works Differently

  • Migrations — In browsers, migrations run automatically on startup
  • Database — IndexedDB in browsers, SQLite/PostgreSQL on servers
  • No ActiveRecord queries — Use where, find, all—no raw SQL

What Doesn’t Work

  • Complex associations — has_many :through is limited
  • Callbacks — after_save works; around_* callbacks don’t
  • Scopes — Lambda scopes need explicit conversion

Next Steps

Back to Juntos/demos