According to MDN it is expected to be an actual comparator: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort#descript

According to MDN it is expected to be an actual comparator: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort#description:~:text=More%20formally%2C%20the%20comparator%20is%20expected%20to%20have%20the%20following%20properties https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... The specification says that if the comparator is not a consistent comparator, the sort order is implementation defined: https://tc39.es/ecma262/multipage/indexed-collections.html#sort-order https://tc39.es/ecma262/multipage/indexed-collections.html#s... Further along, it is specified that only if the sort order is correct, are you guaranteed to get a permutation of the input as the result. I would not write code expecting this to work.