ESM only packages

#todo - break this down into a few more zettles

• what type: module does on its own
• why TS needs file extensions now

ESM is a much more modern standard, and given the complexity of [[20250627030527-cjs-esm-bundling]], some maintainers are opting to produce ESM only packages.

Error [ERR_REQUIRE_ESM]: require() of ES Module esm-only-package not supported.

When using a ESM package, you cannot require the package, leaving you with a few options:

1. Use type: module in your application (package.json)
   1. This tells Node to interpret .js files within this package as ESM, rather than the default CJS
2. Use await import
3. Use Node 22, which can require ESM packages

To ensure your Typescript project is using ESM properly, you may need to change module and moduleResolution to newer values, such as nodenext.

Additionally there's some weirdness around using file extensions in imports which I don't fully understand yet. I believe you need to explicitly add .js imports, as that's what your compiled code would point to. https://www.totaltypescript.com/relative-import-paths-need-explicit-file-extensions-in-ecmascript-imports There's also allowImportingTsExtensions as a config option.

https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c https://antfu.me/posts/publish-esm-and-cjs#compatibility

[[20250627030527-cjs-esm-bundling]] [[20250627100132-js-module-types]]

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