import React from 'react';
import ReactDOM from 'react-dom';

class App extends React.Component {
   constructor() {
      super();

      this.state = {
         data: []
      }

      this.setStateHandler = this.setStateHandler.bind(this);
      this.forceUpdateHandler = this.forceUpdateHandler.bind(this);
   };

   setStateHandler() {
      var item = "setState..."
      var myArray = this.state.data.slice();
	  myArray.push(item);
      this.setState({data: myArray})
   };

   forceUpdateHandler() {
	   this.state.data = [];
      this.forceUpdate();
   };

   render() {
      return (
         <div>
            <button onClick = {this.setStateHandler}>setState</button>
            <button onClick = {this.forceUpdateHandler}>foreceUpdate</button>
            <h4>State Array: {this.state.data}</h4>
         </div>
      );
   }
}

ReactDOM.render(<App />, document.getElementById('root'));