shakacode/react_on_rails

# Server Rendering Tips

For the best performance with Server Rendering, consider using [React on Rails Pro]


## General Tips
- Your code can't reference `document`. Server side JS execution does not have access to `document`,
  so jQuery and some other libs won't work in this environment. You can debug this by putting in
  `console.log` statements in your code.
- You can conditionally avoid running code that references document by either checking if `window`
  is defined or using the "railsContext" 
  your top level react component. Since the passed in props Hash from the view helper applies to
  client and server side code, the best way to do this is to use a Render-Function.
- If you're serious about server rendering, it's worth the effort to have different entry points for client and server rendering. It's worth the extra complexity. The point is that you have separate files for top level client or server side, and you pass some extra option indicating that rendering is happening server side.
- You can enable Node.js server rendering via [React on Rails Pro](https://github.com/shakacode/react_on_rails/wiki).

## Troubleshooting Server Rendering

1. First be sure your code works with server rendering disabled (`prerender: false`)
2. Be sure that `config.trace` is true. You will get the server invocation code that renders your component. If you're not using Shakapacker, you will also get the whole file used to setup the JavaScript context.

## CSS
Server bundles must always have CSS Extracted

## setTimeout, setInterval, and clearTimeout

These methods are polyfilled for server rendering to be no-ops. We log calls to these when in `trace` mode. In the past, some libraries, namely babel-polyfill, did call setTimout. 

Here's an example of this which shows the line numbers that end up calling setTimeout:
```
➜  ~/shakacode/react_on_rails/gen-examples/examples/basic-server-rendering (add-rails-helper-to-generator u=) ✗ export SERVER_TRACE_REACT_ON_RAILS=TRUE
➜  ~/shakacode/react_on_rails/gen-examples/examples/basic-server-rendering (add-rails-helper-to-generator u=) ✗ rspec 
Hello World
Building Webpack client-rendering assets...
Completed building Webpack client-rendering assets.
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
react_renderer.rb: 92
wrote file tmp/server-generated.js
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
react_renderer.rb: 92
wrote file tmp/base_js_code.js
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
[SERVER] setTimeout is not defined for execJS. See https://github.com/sstephenson/execjs#faq. Note babel-polyfill will call this.
[SERVER] at setTimeout (<eval>:31:17)
at defer (<eval>:4422:8)
at setImmediate (<eval>:4387:6)
at notify (<eval>:4481:16)
at module.exports (<eval>:4490:6)
at notify (<eval>:4081:4)
at Promise.$resolve (<eval>:4189:8)
at <eval>:793:18
at Function.resolve (<eval>:4265:6)
  the hello world example works
```