web-worker

Native cross-platform Web Workers. Works in published npm modules.

In Node, it's a web-compatible Worker implementation atop Node's worker_threads.

In the browser (and when bundled for the browser), it's simply an alias of Worker.

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_Here's how this is different from worker_threads:_

- makes Worker code compatible across browser and Node
- supports Module Workers ({type:'module'}) natively in Node 12.8+
- uses DOM-style events (Event.data, Event.type, etc)
- supports event handler properties (worker.onmessage=..)
- Worker() accepts a module URL, Blob URL or Data URL
- emulates browser-style [WorkerGlobalScope] within the worker

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In its simplest form:

``js
import Worker from 'web-worker';

const worker = new Worker('data:,postMessage("hello")');
worker.onmessage = e => console.log(e.data); // "hello"
`

👉 Notice how new URL('./worker.js', import.meta.url) is used above to load the worker relative to the current module instead of the application base URL. Without this, Worker URLs are relative to a document's URL, which in Node.js is interpreted to be process.cwd().

> _Support for this pattern in build tools and test frameworks is still limited. We are working on growing this._

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Module Workers are supported in Node 12.8+ using this plugin, leveraging Node's native ES Modules support.
In the browser, they can be used natively in Chrome 80+, or in all browsers via [worker-plugin] or [rollup-plugin-off-main-thread]. As with classic workers, there is no difference in usage between Node and the browser:

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Instantiating Worker using a Data URL is supported in both module and classic workers:

`js
import Worker from 'web-worker';

const worker = new Worker(data:application/javascript,postMessage(42));
worker.addEventListener('message', e => {
console.log(e.data) // 42
});
`

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This module aims to provide a simple and forgettable piece of infrastructure,
and as such it needed an obvious and descriptive name.
@calvinmetcalf, who you may recognize as the author of Lie and other fine modules, gratiously offered up the name from his web-worker` package.
Thanks Calvin!

[worker-plugin]: https://github.com/googlechromelabs/worker-plugin
[rollup-plugin-off-main-thread]: https://github.com/surma/rollup-plugin-off-main-thread
[WorkerGlobalScope]: https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope