As we saw in the previous exercise, state reacts to reassignments. But it also reacts to mutations — we call this deep reactivity.

Make numbers a reactive array:

let numbers = $state([1, 2, 3, 4]);

Now, when we change the array...

function addNumber() {
	numbers[numbers.length] = numbers.length + 1;
}

...the component updates. Or better still, we can push to the array instead:

function addNumber() {
	numbers.push(numbers.length + 1);
}

Deep reactivity is implemented using proxies, and mutations to the proxy do not affect the original object.