Since upgrading to React 16 I get this error message:
warning.js:33 Warning: Expected server HTML to contain a matching
I'm assuming you are using ssr. The warning is about attempting to render before there is a window object. You need to hydrate.
ReactDOM.hydrate( , document.getElementById("home"))
What I don't understand, is that the App component is being served static by express. Why is it trying to render before it is served? Bring on the comments.