Troubleshooting

TypeError when using React: Cannot read property 'firstChild' of undefined

This error is commonly caused by two versions of React loaded alongside.

For example, if you npm install a package that requires a different React version and puts it into dependencies instead of peerDependencies, it might install a separate React into node_modules/<some library using React>/node_modules/react.

Two different Reacts won't play nicely together (at least yet).

To fix it, just delete node_modules/<some library using React>/node_modules/react. If you see a library putting React in dependencies instead of peerDependencies, file an issue.

See more: http://stackoverflow.com/questions/27153166/typeerror-when-using-react-cannot-read-property-firstchild-of-undefined?answertab=votes#tab-top