I like the method chain and find it very readable (and a good guarantor of typed output in the absence of strict types, if you use something like Typescript to lint it). But I don't see how the choice between that or a pipe operator has any impact on whether function main() should be your program's entry point. Unless your program is going to be an endless loop, e.g. a Nodejs server or else a game, I don't know why you'd want to saddle yourself with a main() every time it runs.