I am using React Hooks
to get data from an existing API. Here is my code
import React, { useState, useEffect } from "react";
export const People = () => {
const [people, setPeople] = useState([]);
const url = "http://127.0.0.1:5000/people";
async function fetchData() {
console.log("calling api .. ");
const res = await fetch(url);
res.json().then((res) => setPeople(res));
}
useEffect(() => {
fetchData();
});
return (
<div>
<ul>
{people &&
people.map((person) => <li key={person.id}>{person.name}</li>)}
</ul>
</div>
);
};
const Dashboard = (props) => {
return (
<div>
<People />
</div>
);
};
export default Dashboard;
The problem that I am having is this API is getting called over and over again. Can you please let me know what I am doing wrong here.
Thanks
Currently, using useEffect(callback)
will execute the callback on every render .
Try using useEffect
with an empty dependencies array .
If you want to run an effect and clean it up only once , you can pass an empty array (
[]
) as a second argument. This tells React that your effect doesn't depend on any values from props or state, so it never needs to re-run .
useEffect
use cases.useEffect(() => {
fetchData();
}, []);
As for the rest of the component, it should look like so (opinioned):
// Should be on the outer scope as the URL is decoupled from the component's logic
const url = "http://127.0.0.1:5000/people";
export const People = () => {
const [people, setPeople] = useState([]);
useEffect(() => {
// This way fetchData won't re-assigned on every render
async function fetchData() {
console.log("calling api .. ");
const res = await fetch(URL);
// Consitstance, don't mix `then` and `await` syntax
const people = await res.json();
setPeople(people);
}
fetchData();
}, []);
return (
<div>
<ul>
{people &&
people.map((person) => <li key={person.id}>{person.name}</li>)}
</ul>
</div>
);
};
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