React - How do I get fetched data outside of an async function? - reactjs

Question

I'm trying to get the data of "body" outside of the fetchUserData() function.
I just want to store it in an variable for later use.
Also tried modifying state, but didn't work either.
Thanks for your help :)
const [userData, setUserData] = useState();
async function fetchUserData () {
try {
const result = await fetch(`/usermanagement/getdocent`, {
method: "GET"
});
const body = await result.json();
//setUserData(body);
return(
body
)
} catch (err) {
console.log(err);
}
}
let userTestData
fetchUserData().then(data => {userTestData = data});
console.log(userTestData);
//console.log(userData);

Answer 1

Use useEffect
async function fetchUserData () {
try {
const result = await fetch(`/usermanagement/getdocent`, {
method: "GET"
})
return await result.json()
} catch (err) {
console.log(err)
return null
}
}
const FunctionalComponent = () => {
const [userData, setUserData] = useState()
useEffect(() => {
fetchUserData().then(data => {
data && setUserData(data)
})
}, []) // componentDidMount
return <div />
}
Ben Awad's awesome tutorial
Example:

Answer 2

it seems that you are making it more complicated than it should be. When you get the response i.e the resolved promise with the data inside the async function, just set the state and in the next render you should get the updated data.
Example:
const [userData, setUserData] = useState();
useEffect(() => {
const getResponse = async () => {
try {
const result = await fetch(`/usermanagement/getdocent`, {
method: "GET"
});
const body = await result.json();
setUserData(body);
} catch (err) {
console.log(err)
}
}
getResponse();
}, [])
console.log(userData);
return <div></div>
Assuming the you need to call the function only once define and call it inside a useEffect or 'componentDidMount'. For using async function inside useEffect we need to define another function and then call it.

Answer 3

When you do
let userTestData
// This line does not wait and next line is executed immediately before userTestData is set
fetchUserData().then(data => {userTestData = data});
console.log(userTestData);
// Try changing to
async someAsyncScope() {
const userTestData = await fetchUserData();
console.log(userTestData)
}
Example:
state = {
someKey: 'someInitialValue'
};
async myAsyncMethod() {
const myAsyncValue = await anotherAsyncMethod();
this.setState({ someKey: myAsyncValue });
}
/*
* Then in the template or where ever, use a state variable which you update when
* the promise resolves. When a state value is used, once the state is updated,
* it triggers as a re-render
*/
render() {
return <div>{this.state.someKey}</div>;
}
In your example you'd use setUserData instead of this.setState and userData instead of {this.state.someKey}