EN
React - async useEffect
3 points
In this article we would like to show you how to use async useEffect in React.
Note: to see how to create custom async
useEffecthook read this article.
In below example we create additional internal async function for useEffect call. We can't use async directly because it will make the callback function return a Promise instead of cleanup function.
Runnable example:
xxxxxxxxxx1
//Note: Uncomment import lines during working with JSX Compiler.2
// import React from "react";3
// import ReactDOM from "react-dom";4
5
const App = () => {6
const [response, setResponse] = React.useState();7
React.useEffect(() => {8
let mounted = true; // to let make state changes only when component is mounted9
; (async () => {10
const requestText = 'hello';11
try {12
const response = await fetch(`/examples/echo?text=${encodeURIComponent(requestText)}`);13
const responseText = await response.text();14
if (mounted) {15
setResponse(`Response: ${responseText}`);16
}17
} catch (error) {18
if (mounted) {19
setResponse('Request error!');20
}21
}22
})();23
return () => {24
mounted = false;25
};26
}, []);27
return (28
<div>{response}</div>29
);30
};31
32
const root = document.querySelector('#root');33
ReactDOM.render(<App />, root);Note:
So do not use following construction because it doesn't allow us to detect component unmount action:
xxxxxxxxxx1React.useEffect(async () => {}, []);
