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Barrel File

Given the directory structure:

lib
|-index.ts
|-helpers
  |-someHelper.ts
  |-otherHelper.ts
  |-formatSomething.ts
  |-getSomething.ts
  |-index.ts
|-service
  |-someHook.ts
  |-otherFile.ts

lib/helpers/index.ts would look like this:

// default exports
import someHelper from "./someHelper";
import formatSomething from "./formatSomething";

// named exports
export * from "./otherHelper";
export * from "./getSomething";

// default exports need to be re-exported
export {
  someHelper,
  formatSomething,
}

lib/index.ts (main export of the library) would look like this:

export * from "./helpers"

Consumers should exclusively import from the main export of the library.

  • Do NOT import from any other file of the library as an external consumer
  • Same pattern as released NPM packages
// do NOT:
import { someFunction } from "lib/package/src/nested/directory"

// do instead:
// external packages:
import { someFunction } from "@public-entrypoint"
import { someFunction } from "@publicSymbol"
// internal packages/libraries:
import { someFunction } from "public-interface"
import { someFunction } from "library-name"

When using external projects, only use public interfaces.

  • Since you don't have control over the internal structures, do NOT rely on them.
  • Allows for quick pivot when you need to switch away from the external library.
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