> One of my major gripes with the JS/TS ecosystem is that "explanations" are sorely lacking. See https://www.typescriptlang.org/tsconfig for the relevant documentation for tsconfig files. Tutorials are on the page, how-to guides abound on the wider internet (like the OP), and the linked TSConfig Reference and JSON Schema (used in code completion in IDEs) are together absolutely massive.

> But an explanation is missing! There is no official documentation about how different options interact to say: as I'm walking a file tree as the Typescript compiler, this is how I will interpret a certain file I encounter, what will be outputted, and how that will be interpreted by bundlers and browsers, especially in an ESM world.

Perhaps you missed it, but Andrew (from the TS team) recently finished a massive overhaul of our module docs: https://www.typescriptlang.org/docs/handbook/modules/introdu...

The "theory" page describes TypeScript's perspective on modules. The "reference" page documents things from the "as I'm walking a file tree" perspective (among many other details). The "guides" page also provides recommendations for certain kinds of projects.