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Typescript's lib includes "esnext"

See original GitHub issue

Hello, I am confused by "esnext" in lib for TypeScript.

"lib": [
	"dom",
	"dom.iterable",
	"esnext"
],

Does this mean I can use e.g. flatMap? Who provides the polyfill?

Background: I am in the process of migration from CRA-TS to CRA2. Previously we implemented our own flatMap and used es6 as library.

Issue Analytics

State:
Created 4 years ago
Comments:5 (2 by maintainers)

Top GitHub Comments

1reaction

ianschmitzcommented, Apr 13, 2019

The behavior of lib is no different than using the TypeScript compiler by itself. It only specifies which APIs that you “claim” will be available at runtime. This means you can use things like Map, Set, Promise, etc and TypeScript will know what those APIs are. You can customize lib to suit your project.

lib doesn’t provide any polyfills. You will need to do that separately depending on the APIs you’re using and your target browsers. As a side note the TypeScript compiler isn’t used in CRA to compile code, and is only used for type checking.

0reactions

alamothecommented, Apr 13, 2019

Thanks for detailed explanation! Back to es6 for me… the future is still not there 😃

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