Server Rendering Tips

Be sure to use mini_racer. See issues/428

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 passing in a boolean prop to 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 generator 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.
  • You can enable node server rendering if you want. See more information here: https://github.com/shakacode/react_on_rails/blob/master/docs/additional-reading/node-server-rendering.md

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.

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 Webpacker, you will also get the whole file used to setup the JavaScript context.

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

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