So I\'ve been building an app that uses the Fetch API to make a request. Unfortunately, I think the code shown in the Facebook docs are (may be?) incorrect.
I saw a problem like yours. It's not about your code. Are using the app in the Remote JS debugging
mode? If so, disable it. If it didn't work, try to install a release version.
(Posted on behalf of the OP).
Apparently it was due to running the app in debug mode. Running the app with this.setState works just fine when not in debug mode.