workerize-loader  

> A webpack loader that moves a module and its dependencies into a Web Worker, automatically reflecting exported functions as asynchronous proxies.

- Bundles a tiny, purpose-built RPC implementation into your app
- If exported module methods are already async, signature is unchanged
- Supports synchronous and asynchronous worker functions
- Works beautifully with async/await
- Imported value is instantiable, just a decorated Worker

Install

``sh
npm install -D workerize-loader
`

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worker.js:

`js
// block for time ms, then return the number of loops we could run in that time:
export function expensive(time) {
let start = Date.now(),
count = 0
while (Date.now() - start < time) count++
return count
}
`

index.js: _(our demo)_

`js
import worker from 'workerize-loader!./worker'

let instance = worker() // new is optional

instance.expensive(1000).then( count => {
console.log(Ran ${count} loops)
})
`

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#### inline

Type: Boolean
Default: false

You can also inline the worker as a BLOB with the inline parameter

`js
// webpack.config.js
{
loader: 'workerize-loader',
options: { inline: true }
}
`
or
`js
import worker from 'workerize-loader?inline!./worker'
`

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If you're using Babel in your build, make sure you disabled commonJS transform. Otherwize, workerize-loader won't be able to retrieve the list of exported function from your worker script :
`js
{
test: /\.js$/,
loader: "babel-loader",
options: {
presets: [
[
"env",
{
modules: false,
},
],
]
}
}
`

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Workerize-loader supports browsers that support Web Workers - that's IE10+.
However, these browsers require a polyfill in order to use Promises, which Workerize-loader relies on.
It is recommended that the polyfill be installed globally, since Webpack itself also needs Promises to load bundles.

The smallest implementation is the one we recommend installing:

npm i promise-polyfill

Then, in the module you are "workerizing", just add it as your first import:

`js
import 'promise-polyfill/src/polyfill';
`

All worker code can now use Promises.

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To test a module that is normally imported via workerize-loader when not using Webpack, import the module directly in your test:

`diff
-const worker = require('workerize-loader!./worker.js');
+const worker = () => require('./worker.js');

const instance = worker();
`

To test modules that rely on workerized imports when not using Webpack, you'll need to dig into your test runner a bit. For Jest, it's possible to define a custom transform that emulates workerize-loader on the main thread:

`js
// in your Jest configuration
{
"transform": {
"workerize-loader(\\?.)?!(.)": "/workerize-jest.js"
}
}
`

... then add the workerize-jest.js shim to your project:

`js
module.exports = {
process(src, filename, config, options) {
return 'module.exports = () => require(' + JSON.stringify(filename.replace(/.+!/,'')) + ')';
},
};
`

Now your tests and any modules they import can use workerize-loader!` prefixes.

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The inner workings here are heavily inspired by worker-loader. It's worth a read!

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MIT License © Jason Miller