Why the target is set to esnext and the lib to es6?

[Hatko]

Question

In our team, we're trying to mimic the tsconfig you created. Did you have any reasoning behind setting these particular versions for target (esnext) and lib(es6)?

[radko93]

There is no much behind it, as this is only being used for type checking. Feel free to ask other questions if you have any.

[Hatko]

@radko93 I see 🙂

esnext provides more features, which are not necessarily available for es6 (flatMap on an array, for example). Moreover, as I understand, the compiler will make esnext version anyway, as it's specified for the target.
That's why I'm curious why they aren't both set to esnext.

If there is no difference, would it make sense to make it consistent?

[radko93]

I think it can be set to esnext, feel free to open a PR. It makes no difference because it's Metro bundler and babel that actually transpile the code.

[LinusU]

The reason why target and lib is set to different is because Metro will use Babel to transpile the syntax, which is what target controls.

On the other hand, lib specifies which part of the standard library exists, which isn't handled by Babel.

e.g. "syntax": "esnext" will allow you to use async function and await, which Babel can transpile. On the other hand, "lib": "esnext" will allow you to use BigInt, which will then fail at runtime because BigInt isn't supported...