what does this.setState do 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: props and state react

function tick() {
  const element = (
    

      
Hello, world!
      
It is {new Date().toLocaleTimeString()}.
    
  );
  ReactDOM.render(    element,    document.getElementById('root')  );}

setInterval(tick, 1000);