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 react
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>
);
}
}setstate in react
Functional Component
const [counter, setCounter] = useState(0);
setCouter(counter + 1);react lifecycle example
class Test extends React.Component {
constructor() {
console.log('Constructor')
super();
this.state = {
count: 0
};
}
componentDidMount() {
console.log("component did mount");
}
componentDidUpdate() {
console.log("component did update");
}
onClick = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
console.log("render");
return (
<div>
Hello Test
<button onClick={this.onClick}>
{this.state.count}
</button>
</div>
);
}
}
//--for first time
//Constructor
//render
//component did mount
//--for any update
//render
//component did updatereact setState
incrementCount() {
// Note: this will *not* work as intended.
this.setState({count: this.state.count + 1});
}
handleSomething() {
// Let's say `this.state.count` starts at 0.
this.incrementCount();
this.incrementCount();
this.incrementCount();
// When React re-renders the component, `this.state.count` will be 1, but you expected 3.
// This is because `incrementCount()` function above reads from `this.state.count`,
// but React doesn't update `this.state.count` until the component is re-rendered.
// So `incrementCount()` ends up reading `this.state.count` as 0 every time, and sets it to 1.
// The fix is described below!
}Copyright © 2021 Codeinu
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