🚀 Feature Request: Detect whether code is being run in Cloudflare Workers (or Node.js)

Describe the solution

Add some kind of macro to detect whether the code, that is currently being run, is running in Cloudflare Workers.

For example with esbuild:

return esbuild.build({
  define: {
    IS_CLOUDFLARE_WORKER: 'true'
  }
})

I’ve been using this for my custom Cloudflare Worker bundling (see github.com/brillout/build-worker/tree/build-worker.mjs#L20-L22).

[WalshyDev]

I believe the Navigator API is the preferred way to do this

if (navigator.userAgent === 'Cloudflare-Workers') {
  // logic
}

[petebacondarwin]

I just tried this in a worker:

export default {
  async fetch() {) {
    return new Response(JSON.stringify(navigator));
  }
}

and in the browser, I see:

{"userAgent":"Cloudflare-Workers"}