The this Keyword
this isn't fixed by where a function is written - it's decided by how the function is called.
Unlike most variables, `this` is not determined by lexical scope - it's determined at call time, by how a function is invoked. Called as `obj.method()`, `this` is `obj`. Called as a plain function, `this` is `undefined` in strict mode (or the global object otherwise). `call`, `apply`, and `bind` let you set `this` explicitly. Arrow functions are the one exception: they don't have their own `this` at all - they capture `this` lexically from whatever scope they were defined in.
greet is called as user.greet(), so this is user. greetLater is an arrow function - it has no this of its own, so it uses this from the surrounding (module/global) scope, where name doesn't exist.