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We originally had grand plans for using this Event concept for more but
now it's only meant to be used in combination with effects.
It's an Event in the FRP terms, that is triggered from an Effect.
Technically it can also be from another function that itself is
triggered from an existing side-effect but that's kind of an advanced
case.
The canonical case is an effect that triggers an event:
```js
const onHappened = useEffectEvent(() => ...);
useEffect(() => {
onHappened();
}, []);
```
The error code system substitutes React's error messages with error IDs to provide a better debugging support in production. Check out the blog post here.
codes.jsoncontains the mapping from IDs to error messages. This file is generated by the Gulp plugin and is used by both the Babel plugin and the error decoder page in our documentation. This file is append-only, which means an existing code in the file will never be changed/removed.extract-errors.jsis an node script that traverses our codebase and updatescodes.json. You can test it by runningyarn extract-errors. It works by crawling the build artifacts directory, so you need to have either run the build script or downloaded pre-built artifacts (e.g. withyarn download build). It works with partial builds, too.transform-error-messagesis a Babel pass that rewrites error messages to IDs for a production (minified) build.