As you can see you have the same mechanism for both worker-to-main and main-to-worker messages.

• the postMessage method for sending messages
• the onmessage member for defining the handler that receives the messages

In the main script:

worker.postMessage(data);

In the worker script:

self.addEventListener("message", function(e) {
    // the passed-in data is available via e.data
}, false);

… or just…

onmessage = function(e) {
    // the passed-in data is available via e.data
};