# [J], 14 bytes [:,]`toupper/. [Try it online!][TIO-kxxw4c89] [J]: http://jsoftware.com/ [TIO-kxxw4c89]: https://tio.run/##y/qvpKeepmBrpaCuoKNgoGAFxLp6Cs5BPm7/o610YhNK8ksLClKL9PX@a3KlJmfkK6QpqCemZuaXqv8HAA "J – Try It Online" - ``]`toupper/.`` In general, ``u`v/.`` will alternately apply verb `u` and `v` to each element in a list. Here, we alternately apply the identity `]` and `toupper`. - `[:,` The above will return a 1-column matrix, though. So we need to flatten `,` the result.