class Addgrocery extends React.Component{
  constructor(props) {
    super(props);
    this.state = {
      count : 0;
    }
}

addgrcy =() => {
  this.setState({
    number: this.state.number +1
  });
}

render(){
  return (
    <div>
     <h1>counter</h1>
     <div>{this.state.count}</div>
     <button onClick={this.addgrcy}>+</button>
    </div>
   );
  }
 }