Spread Syntax
Take an array or object (or other iterable) and expand its items into their own individual values.
let sandwiches = ['tuna', 'turkey', 'pb&j'];
// logs ["tuna", "turkey", "pb&j"]
console.log(sandwiches);
// logs tuna turkey pb&j
console.log(...sandwiches);
You can use it to pass array values into a function.
let numbers = [4, 2];
// Instead of this...
add(numbers[0], numbers[1]);
// You can do this...
add(...numbers);
You can also use to copy or merge arrays or objects.
let moreSandwiches = [...sandwiches1, ...sandwiches2];
let allWizards = {...radagast, ...gandalf};