reactのサンプルコード　setStateとかpropsとかeventの渡しかたとか　

App.js

import React, { Component } from 'react';

class App extends Component {
    constructor(props){
      super(props);
      this.state = {text:'hello'};
    }

    changeText(event){
      console.log(event.target.value);
      this.setState({text:event.target.value});
    }

  render() {

    return (

        <div>
            <TextView value = {this.state.text}/>
            <input type="text" onChange={(event)=>{this.changeText(event)}}/>
        </div>
   );
  }
}

const TextView = (props) => {
  return (
      <div>{props.value}</div>
      );
}

export default App;