What do these three dots in React do?

Question

What does the ... do in this React (using JSX) code and what is it called?

Answer 1

Those are called spreads. Just as the name implies. It means it's putting whatever the value of it in those array or objects.

Such as :

let a = [1, 2, 3];
let b = [...a, 4, 5, 6];
console.log(b);
> [1, 2, 3, 4, 5, 6]