Non-blocking Asynchronous JSON.parse Using The Fetch API

I am working on Swagger Editor performance. One of the solutions to speed things up was moving process-intensive task to Web Workers. Web Workers do a great job of moving process-heavy tasks out of the main thread but the way we can communicate with them is very slow. For each message to be sent to or received from a worker we need to convert it to a string. This means for transferring objects between the main thread and worker threads we need to JSON.parse and JSON.stringify our objects back and forth. For larger objects, this can lead to large blocking JSON.parse calls. For example, when transferring back the AST from our AST-composer worker I saw a 50ms pause. A 50 millisecond pause can easily drop 4 frames.