Sort a table by several columns

Click a table header and you sort by one column. Shift-click another and you sort by both: the second column only breaks ties in the first. Writing that as a single comparator is the trick.

Implement sortBy(items, sorts). items is an array of objects. sorts is an array of { key, direction } objects, applied in order: the first entry is the primary sort, the second breaks its ties, and so on. direction is either "asc" or "desc", and defaults to ascending when it is absent. Compare values with the < and > operators, so numbers sort numerically and strings sort lexicographically. Return a new array; the input must not be reordered. The sort is stable: items that compare equal on every key stay in their original relative order. An empty sorts array returns a copy of items in its original order.

sortBy(
  [
    { name: "Ana", score: 8 },
    { name: "Bo",  score: 10 },
    { name: "Cy",  score: 8 },
  ],
  [{ key: "score", direction: "desc" }, { key: "name" }],
);
// [{ Bo, 10 }, { Ana, 8 }, { Cy, 8 }] — score desc, name asc as tiebreak

sortBy([{ n: 3 }, { n: 1 }, { n: 2 }], []);
// [{ n: 3 }, { n: 1 }, { n: 2 }] — no sorts means the original order