Ive had a hard time adjusting to arrow functions for some reason.
<!--old es5 javascript -->
function (x) { return x + 1 }
function (x,y) { return x + y }
<!-- new es6 syntax -->
x => { x + 1 }
(x,y) => { x + y }
If you remember input => output, that should make it click for you.
Just remember:
(this input) => { gives me this output }
Why dont you check out .map .filter and .foreach next?