ScriptdrillSort by several keys
A JavaScript exercise from Scriptdrill. Solve it with a code editor in your browser that runs your function against example and hidden tests, and it is checked the moment you submit.
The task
Return a sorted copy of `items`. `keys` lists field names in priority order; a leading minus sign, like `"-salary"`, sorts that field from high to low. Numbers compare as numbers and strings with `<` and `>`. Items that tie on every key keep their original order. Do not change `items`.
What this exercise teaches
The comparator checks each key in turn and returns as soon as one decides the order; the minus sign flips the sign of the result. Comparing with < and > keeps numbers numeric, where converting to strings would put 100 before 9.
A hint if you get stuck
Copy with `[...items]`, then `sort` with a comparator that walks the keys and returns at the first key where two items differ. `Array.prototype.sort` is stable, so ties stay in order.
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