First off, great work you are doing with esbuild!

We still have to support Edge 18 and we are running into a problem with our ServiceWorker - we cannot register it. This is similar to this SO thread. We used webpack before and hat to lower the target to ES2017.

I tried everything, but esbuild does not replace (all) spread operators in our build. I tried ES2015, edge18 and almost everything in between. :-) The generated code still contains lots of spread operators.

This is my build-config:

    esbuild.buildSync({
        entryPoints: ["ervice_worker.ts"],
        format: "iife",
        tsconfig: "tsconfig.json",
        define: {
            window: "self",
            global: "self",
            // some more project-specific stuff ...
        },
        outdir: "dist",
        sourcemap: "external",
        minifyIdentifiers: false,
        minifySyntax: true,
        minifyWhitespace: true,
        bundle: true,
        external: ["http", "https", "crypto", "stream"],  // we use shared code with NodeJS and remove the imports later on
        target: "es2015",
    })

The resulting code contains array spreads ([...a]), function call spreads (function a(...args)) but afaics no object spreads ({...o}).
Please note: Edge 18 does indeed support array and function call spreads, but service workers on Edge 18 do not.