It's a bit out of fashion, but same thing can be achieved without any extra code using a built-in EventEmitter: let channel = new EventEmitter() await

It's a bit out of fashion, but same thing can be achieved without any extra code using a built-in EventEmitter: let channel = new EventEmitter() await Promise.all([ compile.browser(channel), compile.server(channel) ]) // in compile.browser channel.emit("manifest", assetsManifest) // in compile.server channel.once("manifest", (assetsManifest) => ... ) A new emitter is used each time, so the end result is the same. Curious to hear what others think.