grab utility function

grab.ts

// Grabs a given list of properties from an
// object and returns a new "shrunk" object
// with just those properties while preserving
// correct typing.
function grab<
  O extends { [x in A[number]]: unknown },
  const A extends string[]
>(o: O, properties: A): {
  [x in A[number]]: typeof o[x]
} {
  return Object.fromEntries(
    Object.entries(o).filter(([k, ]) => properties.includes(k))
  ) as O;
}