Cours react js 2

class Saisie extends React.Component{

   constructor(props) {
    super(props);
    this.state = {
      'todos':[]
    };
     this.addTodo = this.addTodo.bind(this);
     this.todoText = React.createRef();
   }

addTodo(event){
  event.preventDefault();
  //this.setState({'todos': [...this.state.todos, this.todoText.current.value]});
  // Ou
  const newItems = this.todoText.current.value;
  this.state.todos.push(newItems);
  this.setState({'todos' : this.state.todos});
  this.todoText.current.value = "";
}
  render(){
          const todos = this.state.todos;
    return (
      <div>
        <ul>{todos.map(todo => <li>{todo}</li>)}</ul>
        <form onSubmit={this.addTodo}>
         <input name="todo" placeHolder="Saisir une action" type ="text" ref={this.todoText}/>
         <input type="submit" value="Ajouter à la liste"/>
          </form>
          </div>
      );
  }
}

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