gistfile1.txt

    const moves = this.state.history.map((step:string[], move:number) => {
    
      const desc = move ? 'Move #' + move : 'Game start';
      return (
        <li>
          <a href="#" key={move} onClick={ () => this.jumpTo(move) } >{move}-{desc}</a>
        </li>
      );
    });
    
    
    
    error: Each child in an array or iterator should have a unique "key" prop. ???