setInterval function without arrow function

Question

I am learning about react components following the documentation https://facebook.github.io/react/docs/state-and-lifecycle.html

Why do we need to use arrow function

Answer 1

setInterval takes function as first argument, in the second case it is getting a returned value

Change it to

this.timerID = setInterval(this.tick.bind(this), 1000);

or

 this.timerID = setInterval(() => this.tick(), 1000);

which is probably what you need when you want to bind the function to the React context.

See this answer on why you need to bind functions in React

If you don't you could have simply written

this.timerID = setInterval(this.tick, 1000);