How to get current logged in user in react js

just wondering how to access the data of a logged in authenticated user in a react js file with node js.

In the handlebar files I have I can see information like this:

I would like to know how to do things like that in a react js file so I can assign the name of the logged in user to a js variable. Something like var name = ;

Thanks in advance and sorry if I've missed something out or said something a tad dense.

via Ed Lynch