setstate react class component code example
Example 1: state with react functions
import React, { useState } from 'react';
function Example() {
// Declare a new state variable, which we'll call "count"
const [count, setCount] = useState(0);
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}
Example 2: set state
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>
)
}
}
Example 3: setstate react js
constructor(props) {
super(props);
this.state = {
isActive: true,
};
}
checkStatus = () => {
this.setState({ // use this function
'isActive' : !this.state.isActive,
});
}
Example 4: lifecycle method react
INITIALIZATION= setup props and state
MOUNTING= constructor->componentWillMount->render->componentDidMount//Birth
UPDATE= shouldComponentUpdate->componentWillUpdate->render
->componentDidUpdate //Growth
UNMOUNTING= componentWillUnmount //Death
Example 5: setstate in react
Functional Component
const [counter, setCounter] = useState(0);
setCouter(counter + 1);
Example 6: 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 ButtonCounter