iframe-worker

A tiny WebWorker polyfill for the file:// protocol in less than 900b

Like pseudo-worker but using an iframe instead of XMLHTTPRequest. This polyfill should be mostly spec-compliant and supports importScripts. It should pretty much be a drop-in replacement, at least for modern browsers which include a constructable EventTarget and Promise._

Installation

npm install iframe-worker

Usage

You can use the polyfill from unpkg.com (recommended):

<script src="https://unpkg.com/iframe-worker/polyfill"></script>

... or bundle the polyfill with your application:

import "iframe-worker/polyfill"

... or use IFrameWorker programmatically:

import { IFrameWorker } from "iframe-worker"

The polyfill will only mount if the document is served via file://.

Caveats

In a WebWorker script, importScripts is a synchronous operation, as it will block the thread until the script was fully loaded and evaluated. This is not supported in an iframe. For this reason, the polyfill for importScripts included with this library will return a Promise, chaining all passed URLs into a sequence, making it awaitable.

Since awaiting anything else than a Promise will wrap the awaited thing into a Promise, calls to importScripts should practically behave the same way for all protocols other than file://. Thus, if you want to make sure that your WebWorker works for all protocols, always await all calls to importScripts.

License

MIT License

Copyright (c) 2020-2022 Martin Donath

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.