lambda-nodejs: Use OutputFormat.ESM by default for .mjs and .ts files

[piotrekwitkowski]

Describe the feature

When my entrypoints are either .mjs and .ts files, I would like the ESM output format to be used by esbuild.

Use Case

Both .mjs and .ts files are written with ES modules in mind. They usually use the export const handler syntax instead of exports.handler. When bundled to CJS, we get a bit of boilerplate in the output which can be prevented by automatically detecting that and using ESM output format.

Proposed Solution

No response

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

CDK version used

2.122.0

Environment details (OS name and version, etc.)

Mac Sonoma