Hmm, I had completely forgotten about that distinction. I also can’t find it in the spec <https://tc39.es/ecma262/ https://tc39.es/ecma262/>, which says that Nu

Hmm, I had completely forgotten about that distinction. I also can’t find it in the spec <https://tc39.es/ecma262/ https://tc39.es/ecma262/>, which says that Number “performs a type conversion when called as a function rather than as a constructor.” <https://tc39.es/ecma262/#sec-number-constructor https://tc39.es/ecma262/#sec-number-constructor>. What this means isn’t spelled out, which seems poor. I would have thought it meant ToNumber <https://tc39.es/ecma262/#sec-tonumber https://tc39.es/ecma262/#sec-tonumber>, but that would throw an exception on BigInt (like unary plus does, <https://tc39.es/ecma262/#sec-unary-plus-operator https://tc39.es/ecma262/#sec-unary-plus-operator>). So now I’m guessing it means ToPrimitive <https://tc39.es/ecma262/#sec-toprimitive https://tc39.es/ecma262/#sec-toprimitive> with preferredType number, which seems to match. This being the case, I believe BigInt is the sole difference between +x and Number(x).