prestate in usestate
const [prevState, setState] = React.useState([]);
setState(prevState => [...prevState, 'somedata'] );
Salo Hopeless
const [prevState, setState] = React.useState([]);
setState(prevState => [...prevState, 'somedata'] );import React, { useEffect } from 'react';
export const App: React.FC = () => {
useEffect(() => {
}, [/*Here can enter some value to call again the content inside useEffect*/])
return (
<div>Use Effect!</div>
);
}// Initialize useState.
const [stateVar, setStateVar] = useState();
// The useState parameters define the default value of stateVar.
useState(); // stateVar === undefined
useState(true); // stateVar === true
useState('Hamburger'); // stateVar === 'Hamburger'
// setStateVar is a function that sets the value of stateVar.
setStateVar(value);
// stateVar is equal to the value that was set in the setStateVar-function.
stateVar
/*
Example usage - Everytime you run toggleActive, the isActive
variable will toggle between false and true.
*/
const [isActive, setIsActive] = useState(false);
function toggleActive() {
setIsActive(!isActive);
}
import { useState } from "react"function ExampleWithManyStates() {
const [age, setAge] = useState(42);
const [fruit, setFruit] = useState('banana');
const [todos, setTodos] = useState([{ text: 'Learn Hooks' }]);function handleOrangeClick() {
// Similar to this.setState({ fruit: 'orange' })
setFruit('orange');
}