Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript React Basics (retired) Designing Data Flow Communicating Events

Uncaught ReferenceError: delta is not defined

Not sure where its gone wrong

var PLAYERS = [
  {
    name: "Graham Morby-Raybould",
    score: 31,
    id: 1,
  },
  {
    name: "Clint Dempsey",
    score: 35,
    id: 2,
  },
  {
    name: "Chris Mcquire",
    score: 42,
    id: 3,
  },
];

function Header(props) {
  return (
    <div className="header">
      <h1>{props.title}</h1>
    </div>
  );
}

Header.propTypes = {
  title: React.PropTypes.string.isRequired,
};


function Counter(props) {
  return (
      <div className="counter">
        <button className="counter-action decrement" onClick={function() {props.onChange(-1);}}> - </button>
        <div className="counter-score"> {props.score} </div>
        <button className="counter-action increment" onClick={function() {props.onChange(1);}}> + </button>
      </div>
    );
  } 

  Counter.propTypes = {
  score: React.PropTypes.number.isRequired,
  onChange: React.PropTypes.func.isRequired,
  }



function Player(props) {
  return (
    <div className="player">
      <div className="player-name">
        {props.name}
      </div>
      <div className="player-score">
        <Counter score={props.score} onChange={props.onScoreChange} />
      </div>
    </div>
  );
}

Player.propTypes = {
  name: React.PropTypes.string.isRequired,
  score: React.PropTypes.number.isRequired,
  onScoreChange: React.PropTypes.func.isRequired,
};

 var Application = React.createClass({
  propTypes: {
    title: React.PropTypes.string,
    initialPlayers: React.PropTypes.arrayOf(React.PropTypes.shape({
      name: React.PropTypes.string.isRequired,
      score: React.PropTypes.number.isRequired,
      id: React.PropTypes.number.isRequired,
    })).isRequired,
  },

  getDefaultProps: function() {
    return {
      title: "Scoreboard",
    }
  },

  getInitialState: function() {
    return {
      players: this.props.initialPlayers,
    };
  },

  onScoreChange: function(index, delta) {
    console.log('onScoreChange' , index , delta);
    this.state.players[index].score += delta;
    this.setState(this.state);
  },

    render: function() {
       return (
        <div className="scoreboard">
          <Header title={this.props.title} />

          <div className="players">
            {this.state.players.map(function(player, index) {
              return (
                <Player
                  onScoreChange={function(){this.onScoreChange(index ,delta)}.bind(this)}
                  name={player.name} 
                  score={player.score} 
                  key={player.id} />
              );
            }.bind(this))}
          </div>
        </div>
      );
    }
  }); 
ReactDOM.render(<Application initialPlayers={PLAYERS}/>, document.getElementById('container'));

1 Answer

Fixed myself!

onScoreChange={function(delta <---- Missing here!){this.onScoreChange(index ,delta)}.bind(this)}