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https://github.com/developit/greenlet
🦎 Move an async function into its own thread.
https://github.com/developit/greenlet
thread web-worker webworker worker workerize
Last synced: 21 days ago
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🦎 Move an async function into its own thread.
- Host: GitHub
- URL: https://github.com/developit/greenlet
- Owner: developit
- Created: 2018-01-26T00:11:57.000Z (almost 7 years ago)
- Default Branch: master
- Last Pushed: 2021-03-01T20:22:52.000Z (over 3 years ago)
- Last Synced: 2024-05-06T10:33:35.357Z (6 months ago)
- Topics: thread, web-worker, webworker, worker, workerize
- Language: JavaScript
- Homepage: https://npm.im/greenlet
- Size: 54.7 KB
- Stars: 4,673
- Watchers: 44
- Forks: 100
- Open Issues: 15
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
- awesome - developit/greenlet
- awesome-list - greenlet
README
## Greenlet [](https://npm.im/greenlet) [](https://travis-ci.org/developit/greenlet) [](https://unpkg.com/greenlet/dist/greenlet.umd.js) [](https://packagephobia.now.sh/result?p=greenlet)
> Move an async function into its own thread.
>
> A simplified single-function version of [workerize](https://github.com/developit/workerize), offering [the same performance as direct Worker usage](https://esbench.com/bench/5b16b61af2949800a0f61ce3).
The name is somewhat of a poor choice, but it was [available on npm](https://npm.im/greenlet).
_Greenlet supports IE10+, since it uses [Web Workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers). For NodeJS usage, Web Workers must be polyfilled using a library like [node-webworker](https://github.com/pgriess/node-webworker)._
## Installation & Usage
```sh
npm i -S greenlet
```
Accepts an async function with, produces a copy of it that runs within a Web Worker.
> ⚠️ **Caveat:** the function you pass cannot rely on its surrounding scope, since it is executed in an isolated context.
```
greenlet(Function) -> Function
```
> ‼️ **Important:** never call greenlet() dynamically. Doing so creates a new Worker thread for every call:
```diff
-const BAD = () => greenlet(x => x)('bad') // creates a new thread on every call
+const fn = greenlet(x => x);
+const GOOD = () => fn('good'); // uses the same thread on every call
```
Since Greenlets can't rely on surrounding scope anyway, it's best to always create them at the "top" of your module.
## Example
Greenlet is most effective when the work being done has relatively small inputs/outputs.
One such example would be fetching a network resource when only a subset of the resulting information is needed:
```js
import greenlet from 'greenlet'
let getName = greenlet( async username => {
let url = `https://api.github.com/users/${username}`
let res = await fetch(url)
let profile = await res.json()
return profile.name
})
console.log(await getName('developit'))
```
[🔄 **Run this example on JSFiddle**](https://jsfiddle.net/developit/mf9fbma5/)
## Transferable ready
Greenlet will even accept and optimize [transferables](https://developer.mozilla.org/en-US/docs/Web/API/Transferable) as arguments to and from a greenlet worker function.
## Browser support
Thankfully, Web Workers have been around for a while and [are broadly supported](https://caniuse.com/#feat=webworkers) by Chrome, Firefox, Safari, Edge, and Internet Explorer 10+.
If you still need to support older browsers, you can just check for the presence of `window.Worker`:
```js
if (window.Worker) {
...
} else {
...
}
```
### CSP
If your app has a [Content-Security-Policy](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy), Greenlet requires `worker-src blob:` and `script-src blob:` in your config.
## License & Credits
> In addition to the contributors, credit goes to [@sgb-io](https://github.com/sgb-io) for his annotated exploration of Greenlet's source. This prompted a refactor that clarified the code and allowed for further size optimizations.
[MIT License](https://oss.ninja/mit/developit)