Sort compare curried function to access obj string properties values

sort.ts

// https://stackoverflow.com/a/61476921/1355416
type FilteredKeys<T, U> = { [P in keyof T]: T[P] extends U ? P : never }[keyof T]

const compareStrings = <T extends object>(key: FilteredKeys<T, string>) => (a: T, b: T): number => {
  const valA = (a[key] as unknown) as string
  const valB = (b[key] as unknown) as string

  return valA.localeCompare(valB)
}

type Example = {
  x: string
  y: number
  z: boolean
}
const example: Example[] = [
  {
    x: 'test',
    y: 42,
    z: true,
  },
  {
    x: 'foo',
    y: 5,
    z: false,
  },
]

// Only allows x, no y or z
export const foo = example.sort(compareStrings('x'))