state and setstate react code example

Example 1: 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 (
      

        

          {this.state.count}
        
        Increment by 1
        Decrement by 1
      
    )
  }
}

Example 2: setstate react js

constructor(props) {
        super(props);
        this.state = {
            isActive: true,
        };
    }

    checkStatus = () => {
        this.setState({		// use this function
            'isActive' : !this.state.isActive,
        });
    }

Example 3: react 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!
}

Example 4: set state

setState({ searchTerm: event.target.value })