setRouteWillLeaveHook provides a method for us to intercept a route change before leaving the current route.
Thanks for these tuts! Really enjoyed it as an intro to React Router. I thought everything was self-explanatory, but I'm left with one question - how did you enable html snippets in your Sublime Text on .js files? Killing me writing
<h1> over and over again hahaha.
Also, were you using custom es6 snippets here or did you get them from a pacakge? I'm currently using https://github.com/babel/babel-sublime-snippets for main React/JSX stuff