Create dynamic lists in React

class App extends React.Component{

  state = {
    lists : {
      'list-1' : 'PHP',
      'list-2' : 'Wordpress'
    }
  }

    addList = (list) => {

      var timestamp = (new Date()).getTime();

      this.state.lists['list-' + timestamp ] = list;

      this.setState({ lists : this.state.lists });
     }

     removeList = (listKey) => {
      delete this.state.lists[listKey];
      this.setState({ lists : this.state.lists });
     }

     render() {
      return (
        <div className="component-wrapper">
          <ItemList lists={this.state.lists} removeList={this.removeList}/>
          <AddListForm addList={this.addList} />
        </div>
       );
      }

     }


     class ItemList extends React.Component{

      render () {
        return (
          <div className="container">
            <ul className="list-group text-center">
              {
                Object.keys(this.props.lists).map(function(key) {
                  return <li className="list-group-item list-group-item-info">{this.props.lists[key]} <span onClick={()=>this.props.removeList(key)}>X</span></li>
                }.bind(this))
              }
            </ul>
           </div>
          );
        }
      }



      class AddListForm extends React.Component{

        createList = (e) => {
          e.preventDefault();

          var list = this.refs.listName.value;

          if(list.length > 0) {
            this.props.addList(list);
          }

          this.refs.listForm.reset();
        }

        render = () => {
          return(
            <form className="form-inline" ref="listForm" onSubmit={this.createList}>
              <div className="form-group">
                <label for="listItem">
                  List Name
                  <input type="text" id="listItem" className="form-control" placeholder="e.x.lemmon" ref="listName" />
                </label>
              </div>
              <button type="submit" className="btn btn-primary">Add List</button>
            </form>
          )

        }
      }

      React.render(
        <App />,
        document.getElementById('app')
      );