Im learning JS and React and I came to the code example below and some parts I don't understand properly. The second.then is inside useUffect is this ok, or it's better to be in getData func? Also in render there is data**?**.map and I don't understand why we need?, is this ternary operator? Is so I thought that ternary operator requires: as a second parameter. Thanks in advance!
import React, { useState, useEffect } from "react";
const FetchData = () => {
const [data, setData] = useState(null);
const fetchURL = "https://jsonplaceholder.typicode.com";
const getData = () => fetch(`${fetchURL}/posts`)
.then((res) => res.json());
useEffect(() => {
getData().then((data) => setData(data));
}, []);
return (<div>
{data?.map(item => (
<ul>
<li>{item.title}</li>
</ul>
))}
</div>);
};
export default FetchData;
I think, your code is fine, Move getData and fetchURL
into useEffect
incase if there's any error.
Also, You can simply use async/await
approach for the same.
import React, { useState, useEffect } from "react";
const FetchData = () => {
const [data, setData] = useState(null) // here you can define `[]` if you don't want to check `?`
useEffect(() => {
const fetchURL = "https://jsonplaceholder.typicode.com";
const getData = async () => {
const res = await fetch(`${fetchURL}/posts`)
const result = await res.json();
setData(result);
}
getData()
}, []);
return (<div>
{data?.map(item => (
<ul>
<li>{item.title}</li>
</ul>
))}
</div>);
};
export default FetchData;
?
is Called Optional Chain Operator , which will help you to check whether the value is nullish (null or undefined)
.
Basically, it just doing if (data) { data.map...}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.