typescript - What does the tsconfig option "lib" do?

Question

I have an existing project that has this line in tsconfig.json:

lib:["2016", "DOM"]

What is the purpose of this?

The only info I could find is this:

Specify library file to be included in the compilation. Requires TypeScript version 2.0 or later.

What does that mean?

Answer 1

This is a new typescript 2 feature and so it still lacks documentation, but you can read about it in the What's new in Typescript 2.0:

with --lib you can specify a list of built-in API declaration groups that you can chose to include in your project. For instance, if you expect your runtime to have support for Map, Set and Promise (e.g. most evergreen browsers today), just include --lib es2015.collection,es2015.promise. Similarly you can exclude declarations you do not want to include in your project, e.g. DOM if you are working on a node project using --lib es5,es6.

There's also a list of the API groups that are supported and a very short example in that link.