react and react-dom package versions have to be in sync. Currently because of the ^ for React, react@v15.4.2 is installed while React DOM doesn't have the ^ and react-dom@v15.3 was installed for me. ReactDOMServer was shifted into react-dom in 15.4, causing an error when I used react-dom@v15.3. Hence the versions of these two packages have to be in sync.
reactandreact-dompackage versions have to be in sync. Currently because of the^for React,react@v15.4.2is installed while React DOM doesn't have the^andreact-dom@v15.3was installed for me.ReactDOMServerwas shifted intoreact-domin 15.4, causing an error when I usedreact-dom@v15.3. Hence the versions of these two packages have to be in sync.