Sum Unknown Numbers

unknown is safer than any, but you must prove or assert its shape. If a value is really a number array, you can assert as number[] to use array methods.

This exercise keeps runtime simple. You will assert and then sum.

const xs: unknown = [1, 2, 3];
const total = (xs as number[]).reduce((a, b) => a + b, 0);

Your Task

Add up the numbers from an unknown value.

• Implement sumUnknown(input: unknown): number.
• Treat input as number[] using an assertion and return the sum.
• If the array is empty, return 0.
• Do not mutate the array.