React introduces a component model to compose your UI. There are a couple of ways of rendering a component/JSX. You can use these simples rules to determine which way to write your component.
With the advent of ES6 and Class fields we can now write shorter components and without the need of worrying with the this keyword bind.
Should one stop using class setState for lack of understanding it.
Advantages of using class fields and Arrow functions
In a recent commit to Relay 1.2, it was added a third argument to refetchConnection, the refetchConnection is an API provided by the createPaginationContainer