He posts the MDN official definitions of concat and push, but doesn't himself say that they are for different cases. The fact that performance is being talked about without real use cases for either is pretty silly. And his final reasoning for when to use what is just going by part of the official definitions. The core difference between them is mutability. And many times the defining reason for using one or the other. #bad_dev #javascript #patterns_moi_smarter_than_give_self_credit #pub