setState

import React, { Component } from 'react';

class App extends Component {  
  constructor(props) {
    super(props);
    this.state = {num:1}
  }
  addNum(){
    this.setState({num:this.state.num+1})
  }
  render() {     
    return (
      

        
{this.state.num}
        {this.addNum()}}>按钮     
      
    );
  }
}

export default App;

 按钮