ExecJS environment defines window

[NGMarmaduke]

• My app crashes with react-rails, so I've included the stack trace and the exact steps which make it crash.

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The ExecJSRenderer defines window as the global scope for server rendering here: ExecJSRenderer:36

This can cause major issues when using 3rd party libraries that perform type of checks on the window variable to detect the presence of a browser environment.

I have created an example Rails app to reproduce the issue:
https://github.com/NGMarmaduke/react-rails-window-example

The sample code with the window check is from yahoo's subscribe-ui-event

The resulting error is:

ExecJS::ProgramError
  ReferenceError: document is not defined

Realistically window shouldn't be defined or available on the server, initial investigation of why this is being defined points me at react-builds/react-server.js, it is assigning variables on the window:

window.React = React;
window.ReactDOM = ReactDOM;
window.ReactDOMServer = ReactDOMServer;

As an aside ReactDOM isn't required for server rendering.