setstate add object to array code example
Example 1: How to add object in an array using useState
import React, { useState } from 'react';
function App() {
const [items, setItems] = useState([]);
// handle click event of the button to add item
const addMoreItem = () => {
setItems(prevItems => [...prevItems, {
id: prevItems.length,
value: getRandomNumber()
}]);
}
// generate 6 digit random number
const getRandomNumber = () => {
return Math.random().toString().substring(2, 8);
}
return (
<div classname="App">
<h3>useState with an array in React Hooks - <a href="https://www.cluemediator.com">Clue Mediator</a></h3>
<br>
<button onclick="{addMoreItem}">Add More</button>
<br><br>
<label>Output:</label>
<pre>{JSON.stringify(items, null, 2)}</pre>
</div>
);
}
export default App;
Example 2: how to update array in react state
this.setState(prevState => ({
arrayvar: [...prevState.arrayvar, newelement]
}))
Example 3: add object to array setstate
To push to the beginning of the array do it this way
this.setState( prevState => ({
userFavorites: [{id: 3, title: 'C'}, ...prevState.userFavourites]
}));