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npm install @n1ru4l/use-async-effect





Simple type-safe async effects for React powered by generator functions.
``tsx
import React from "react";
import useAsyncEffect from "@n1ru4l/use-async-effect";
const MyComponent = ({ filter }) => {
const [data, setData] = React.useState(null);
useAsyncEffect(
function* (onCancel, c) {
const controller = new AbortController();
onCancel(() => controller.abort());
const data = yield* c(
fetch("/data?filter=" + filter, {
signal: controller.signal,
}).then((res) => res.json())
);
setData(data);
},
[filter]
);
return data ?
};
`
- Install Instructions
- The problem
- Example
- Before 😖
- After 🤩
- Usage
- Basic Usage
- Cancel handler (Cancelling an in-flight fetch request)
- Cleanup Handler
- Setup eslint for eslint-plugin-react-hooks
- TypeScript
- API
- useAsyncEffect Hook
- Contributing
- LICENSE
yarn add -E @n1ru4l/use-async-effect
or
npm install -E @n1ru4l/use-async-effect
Doing async stuff with useEffect clutters your code:
- 😖 You cannot pass an async function to useEffect
- 🤢 You cannot cancel an async function
- 🤮 You have to manually keep track whether you can set state or not
This micro library tries to solve this issue by using generator functions:
- ✅ Pass a generator to useAsyncEffectfetch
- ✅ Return cleanup function from generator function
- ✅ Automatically stop running the generator after the dependency list has changed or the component did unmount
- ✅ Optional cancelation handling via events e.g. for canceling your request with AbortController
`jsx
import React, { useEffect } from "react";
const MyComponent = ({ filter }) => {
const [data, setData] = useState(null);
useEffect(() => {
let isCanceled = false;
const controller = new AbortController();
const runHandler = async () => {
try {
const data = await fetch("/data?filter=" + filter, {
signal: controller.signal,
}).then((res) => res.json());
if (isCanceled) {
return;
}
setData(data);
} catch (err) {}
};
runHandler();
return () => {
isCanceled = true;
controller.abort();
};
}, [filter]);
return data ?
};
`
`jsx
import React from "react";
import useAsyncEffect from "@n1ru4l/use-async-effect";
const MyComponent = ({ filter }) => {
const [data, setData] = useState(null);
useAsyncEffect(
function* (onCancel, c) {
const controller = new AbortController();
onCancel(() => controller.abort());
const data = yield* c(
fetch("/data?filter=" + filter, {
signal: controller.signal,
}).then((res) => res.json())
);
setData(data);
},
[filter]
);
return data ?
};
`
Works like useEffect, but with a generator function.
`jsx
import React, { useState } from "react";
import useAsyncEffect from "@n1ru4l/use-async-effect";
const MyDoggoImage = () => {
const [doggoImageSrc, setDoggoImageSrc] = useState(null);
useAsyncEffect(function* (_, c) {
const { message } = yield* c(
fetch("https://dog.ceo/api/breeds/image/random").then((res) => res.json())
);
setDoggoImageSrc(message);
}, []);
return doggoImageSrc ? : null;
};
`

You can react to cancels, that might occur while a promise has not resolved yet, by registering a handler via onCancel.onCancel
After an async operation has been processed, the handler is automatically being unset.
`jsx
import React, { useState } from "react";
import useAsyncEffect from "@n1ru4l/use-async-effect";
const MyDoggoImage = () => {
const [doggoImageSrc, setDoggoImageSrc] = useState(null);
useAsyncEffect(function* (onCancel, c) {
const abortController = new AbortController();
onCancel(() => abortController.abort());
const { message } = yield c(
fetch("https://dog.ceo/api/breeds/image/random", {
signal: abortController.signal,
}).then((res) => res.json())
);
setDoggoImageSrc(message);
}, []);
return doggoImageSrc ? : null;
};
`

Similar to React.useEffect you can return a cleanup function from your generator function.
It will be called once the effect dependencies change or the component is unmounted.
Please take note that the whole generator must be executed before the cleanup handler can be invoked.
In case you setup event listeners etc. earlier you will also have to clean them up by specifiying a cancel handler.
`jsx
import React, { useState } from "react";
import useAsyncEffect from "@n1ru4l/use-async-effect";
const MyDoggoImage = () => {
const [doggoImageSrc, setDoggoImageSrc] = useState(null);
useAsyncEffect(function* (_, c) {
const { message } = yield* c(
fetch("https://dog.ceo/api/breeds/image/random").then((res) => res.json())
);
setDoggoImageSrc(message);
const listener = () => {
console.log("I LOVE DOGGIES", message);
};
window.addEventListener("mousemove", listener);
return () => window.removeEventListener("mousemove", listener);
}, []);
return doggoImageSrc ? : null;
};
`

You need to configure the react-hooks/exhaustive-deps plugin to treat useAsyncEffect as a hook with dependencies.
Add the following to your eslint config file:
`json`
{
"rules": {
"react-hooks/exhaustive-deps": [
"warn",
{
"additionalHooks": "useAsyncEffect"
}
]
}
}
We expose a helper function for TypeScript that allows interferring the correct Promise resolve type. It uses some type-casting magic under the hood and requires you to use the yield* keyword instead of the yield keyword.
`tsx`
useAsyncEffect(function* (setErrorHandler, c) {
const numericValue = yield* c(Promise.resolve(123));
// type of numericValue is number 🎉
});
Runs a effect that includes async operations. The effect ins cancelled upon dependency change/unmount.
`ts``
function useAsyncEffect(
createGenerator: (
setCancelHandler: (
onCancel?: null | (() => void),
onCancelError?: null | ((err: Error) => void)
) => void,
cast:
) => Iterator
deps?: React.DependencyList
): void;
Please check our contribution guides Contributing.
MIT.