Parse can't find localStorage variable in React Native

The answers above are technically right, but Parse has provided a solution that doesn't require a polyfil or downgrading. This was due to my perpetual lack of reading. I found this on the Parse React docs:

As of version 1.6, the Parse JS SDK has a different build for React Native. If you're using Parse+React on React Native, you'll need to require the 'parse-react/react-native' package instead.

For example:

// For React Native apps
var React = require('react-native');
var Parse = require('parse/react-native');
var ParseReact = require('parse-react/react-native');

Sorry for not mentioning I was using Parse React as well. I thought the problem was just with Parse, as I hadn't begun to add data subscriptions via Parse React.

That's correct (with polyfill). There is no localStorage added as polyfill nor the Apple's embedded javascriptCore engine has localStorage implemented (where Chrome's v8 has it implemented of course). Main reason is that localStorage is synchronous and React should only work with asynchronous operations by design.

There is a nice solution/mini-polyfill that replaces localstorage with an in-memory version: https://gist.github.com/juliocesar/926500 . That should let parse use localstorage for cache (that's the main purpose they are using it now I believe). The data will not be persistently stored between application executions. I am not sure if you can disable localstorage use by Parse, but that's another possibility to explore.

I downgraded to 1.5.0 and working now.

"dependencies": {
  "parse": "1.5.0",