Switch to ESM

[jonkoops]

Closes #238

[jonkoops]

Before merging this in we should agree on a strategy in #346.

[dcousens]

@jonkoops if we're compiling anyway, why not TypeScript native? Seeing as we're only 1 file deep for each of the exports, you won't need a bundler either

[dcousens]

I made an example project in https://github.com/dcousens/monorepo-typescript recently which I'm often using as a reference for this kind of project lift, albeit for monorepos

[jonkoops]

if we're compiling anyway, why not TypeScript native? Seeing as we're only 1 file deep for each of the exports, you won't need a bundler either

You are referring to Rollup in the benchmarks directory? I am actually looking to eliminate that entirely after this PR. In theory, all we need is a static file server to be able to import ESM code, which hopefully also eliminates any strange compiler quirks/overhead in the benchmarks.

I think a bundler/compiler (e.g Rollup/TypeScript would make sense if we decide to also support CommonJS next to ESM, but I am not sure if we would want to do so.

Perhaps we merge this in now, and make this a separate point of discussion/log an isssue? WDYT?

[dcousens]

I am not sure if we would want to do so.

We might see slower uptake of 3.0.0 if we opt for ESM only - this consideration is the only thing holding back a merge for me, assuming we don't want to block the next release.

Perhaps we merge this in now, and make this a separate point of discussion/log an isssue? WDYT?

Happy, this is 90% of the work, changing to TS and bundling can easily be a separate discussion, but it needs to be resolved if we want to support CJS.

[remcohaszing]

I think a bundler/compiler (e.g Rollup/TypeScript would make sense if we decide to also support CommonJS next to ESM, but I am not sure if we would want to do so.

Please don't do this. Although many people do so, TypeScript isn't intended to be used for dual publishing. Especially the combination of TypeScript, default exports, and Rollup is a well-known recipe for generating invalid type definitions.

[jonkoops]

Let's continue the CommonJS/TypeScript discussion under #349, and focus on landing this work here.

[jonkoops]

@dcousens WDYT? Can we merge this in?