feck yo

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

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

    this.state = {
      valA: 0,
      arr: []
    };
  }



  update(valA) {
    console.log(valA);

    this.setState({
      valA: valA,
      arr: arr
    });
  }


  addToDo (valA) {
    let self = this;
    let num = self.state.arr.length;
    self.arr[num] = valA;
    this.setState({
      valA: 0,
      arr: self.state.arr
    });
  }


  deleteToDo (place) {
    let self = this;
    for (let i = place ; i < self.state.arr.length ; ++i){
      self.state.arr [i] = self.state.arr[i+1];
    }

    self.state.arr.pop();

    this.setState({
      valA: 0,
      arr: self.state.arr
    });

  }





  render() {
    let self = this;
    let a = <input onKeyUp={ function(e) {self.update(e.target.value);} }/>;
    let b = <button onClick={ self.addToDo }/>;

    let todos = [];

    for (let i = 0 ; i < self.state.arr.length ; ++i ){
      todos[i] = <span> <button onClick={ function(e) {deleteToDo(i);}  }> Удалить заметку</button> </span>;
    }

    return <div>
      {a}
      {b}
      {todos}
    </div>;
  }
}

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