useAsyncEffect


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 ? : null;
};
`

- 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

Install Instructions

yarn add -E @n1ru4l/use-async-effect

or

npm install -E @n1ru4l/use-async-effect

The problem

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 useAsyncEffect
- ✅ 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 fetch request with AbortController

Example

$3

`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 ? : null;
};
`

$3

`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 ? : null;
};
`

Usage

Works like useEffect, but with a generator function.

$3

`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;
};
`

![Edit use-async-effect doggo demo](https://codesandbox.io/s/use-async-effect-doggo-demo-qrqix?fontsize=14)

$3

You can react to cancels, that might occur while a promise has not resolved yet, by registering a handler via onCancel.
After an async operation has been processed, the onCancel 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;
};
`

![Edit use-async-effect doggo cancel demo](https://codesandbox.io/s/use-async-effect-doggo-cancel-demo-6rxvd?fontsize=14)

$3

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;
};
`

![Edit use-async-effect cleanup doggo demo](https://codesandbox.io/s/use-async-effect-doggo-demo-w1zlh?fontsize=14)

$3

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"
}
]
}
}
`

$3

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 🎉
});
`

API

$3

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: (promise: Promise) => Generator, T>
) => Iterator,
deps?: React.DependencyList
): void;
``

Contributing

Please check our contribution guides Contributing.

LICENSE

MIT.