Polyfill for Node that adds support for web Workers.
Just import the polyfill and create Workers as normal:
// index.js
import "node-worker-polyfill";
const worker = new Worker(new URL("worker.js", import.meta.url), { type: "module" });
worker.addEventListener("message", (event) => {
console.log(event.data);
});
worker.postMessage({
text: "Hello world!"
});// worker.js
addEventListener("message", (event) => {
if (event.data.text === "Hello world!") {
postMessage({
text: "Goodbye world!"
});
}
});The polyfill is automatically applied inside of Workers, so you don't need to import it again.
These are the known incompatibilities with the browser:
-
The URL must be a
URLobject, it cannot be a string:// ERROR new Worker("foo.js", { type: "module" })
// Correct new Worker(new URL("foo.js", import.meta.url), { type: "module" })
-
Only the
file://protocol is supported:// ERROR new Worker(new URL("http://foo/"), { type: "module" })
// Correct new Worker(new URL("foo.js", import.meta.url), { type: "module" }) // Correct new Worker(new URL("file:///path/to/foo.js"), { type: "module" })
-
You must use
type: "module":// ERROR new Worker(new URL("foo.js", import.meta.url))
// Correct new Worker(new URL("foo.js", import.meta.url), { type: "module" })
-
This polyfill queues up all messages until the Worker uses
addEventListener:// worker.js await foo(); addEventListener("message", (event) => { console.log(event.data); });
In the browser, the above code will not trigger the
messageevent listener, because the event listener is added afterfoo()finishes, so the messages are simply lost.But with this polyfill, the messages will be queued, so it will trigger the
messageevent listener.This only matters if you delay using
addEventListener, if you useaddEventListenerimmediately then there is no difference with the browser. -
console.logdoes not behave correctly with Workers, this is a known bug with Node.