Three smallest numbers

Write a function threeSmallest(numbers) that returns the three smallest numbers of an array.

• numbers is an array of integers. They can be positive, negative or 0.
• Return a new array with the three smallest numbers, from small to large.
• Equal numbers count separately: [3, 3, 1] gives [1, 3, 3].
• If the array has fewer than 3 numbers, return all of them, from small to large. An empty array gives [].
• Compare the numbers by value: 10 is larger than 9.
• Do not change the input array.

If you sort, keep in mind that sort changes (mutates) the array it is called on and needs a compare function to sort numbers by value.