how to use setstate
class App extends React.Component {
state = { count: 0 }
handleIncrement = () => {
this.setState({ count: this.state.count + 1 })
}
handleDecrement = () => {
this.setState({ count: this.state.count - 1 })
}
render() {
return (
<div>
<div>
{this.state.count}
</div>
<button onClick={this.handleIncrement}>Increment by 1</button>
<button onClick={this.handleDecrement}>Decrement by 1</button>
</div>
)
}
}state with react functions
class Example extends React.Component {
constructor(props) {
super(props);
this.state = {
count: 0
};
}
render() {
return (
<div>
<p>You clicked {this.state.count} times</p>
<button onClick={() => this.setState({ count: this.state.count + 1 })}>
Click me
</button>
</div>
);
}
}lifecycles if reactjs
class Clock extends React.Component {
constructor(props) {
super(props);
this.state = {date: new Date()};
}
componentDidMount() { }
componentWillUnmount() { }
render() {
return (
<div>
<h1>Hello, world!</h1>
<h2>It is {this.state.date.toLocaleTimeString()}.</h2>
</div>
);
}
}setstate in react
Functional Component
const [counter, setCounter] = useState(0);
setCouter(counter + 1);change state in react
import React, {Component} from 'react';
class ButtonCounter extends Component {
constructor() {
super()
// initial state has count set at 0
this.state = {
count: 0
}
}
handleClick = () => {
// when handleClick is called, newCount is set to whatever this.state.count is plus 1 PRIOR to calling this.setState
let newCount = this.state.count + 1
this.setState({
count: newCount
})
}
render() {
return (
<div>
<h1>{this.state.count}</h1>
<button onClick={this.handleClick}>Click Me</button>
</div>
)
}
}
export default ButtonCountercomponent did mmount
componentDidUpdate(prevProps, prevState, snapshot)Copyright © 2021 Codeinu
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