Object keys have a traversal order. Integer keys are always first, and are sorted in an ascending order, whereas with non-integer keys, the order of assignment is preserved. However, this means that sorting will only work on non integer keys, because they are always 1st, and always sorted in an ascending order.

With non-numeric keys like this, you could sort it using entries:

const customers = {
	"_1": "Joe Shmo",
	"_2": "Carrot Top",
	"_3": "Nicolas Cage"
};
const customersArr = Object.entries(customers);
let sorted = customersArr.sort((a, b) => a[1].localeCompare(b[1]));
sorted = Object.fromEntries(sorted);

But, this is really the wrong data-type if you want consistent and easy sorting. Use an array of objects like this and the sorting is much easier.

const customers = [
	{
		id: 1,
		name: "Joe Shmo"
	},
	{
		id: 2,
		name: "Carrot Top"
	},
	{
		id: 3,
		name: "Nicolas Cage"
	}
];
const sorted = customers.sort((a, b) => a.name.localeCompare(b.name));