Hyperapp version of TicTacToe app

TicTacToeHyperapp.js

const { h, app } = hyperapp;
/** @jsx h */

function Square(props) {
  return (
    <button class="square" onclick={props.onClick}>
      {props.value}
    </button>
  );
}

function Board(props) {
  const renderSquare = (i) => (
    <Square value={props.squares[i]} onClick={() => props.onClick(i)} />
  );

  return (
    <div>
      <div class="board-row">
        {renderSquare(0)}
        {renderSquare(1)}
        {renderSquare(2)}
      </div>
      <div class="board-row">
        {renderSquare(3)}
        {renderSquare(4)}
        {renderSquare(5)}
      </div>
      <div class="board-row">
        {renderSquare(6)}
        {renderSquare(7)}
        {renderSquare(8)}
      </div>
    </div>
  );
}

function Game({ state, actions }) {
  const history = state.history;
  const current = history[state.stepNumber];
  const winner = calculateWinner(current.squares);

  let status;
  if (winner) {
    status = "Winner: " + winner;
  } else {
    status = "Next player: " + (state.xIsNext ? "X" : "O");
  }
  const moves = history.map((step, move) => {
    const desc = move ? "Go to move #" + move : "Go to game start";
    return (
      <li key={move}>
        <button
          onclick={() => {
            actions.jumpTo(move);
          }}
        >
          {desc}
        </button>
      </li>
    );
  });

  return (
    <div class="game">
      <div class="game-board">
        <Board
          squares={current.squares}
          onClick={i => actions.handleClick(i)}
        />
      </div>
      <div class="game-info">
        <div>{status}</div>
        <div>{moves}</div>
      </div>
    </div>
  );
}

//A central "state" object
const state = {
  history: [
    {
      squares: Array(9).fill(null)
    }
  ],
  stepNumber: 0,
  xIsNext: true
};

//A central "actions" object. Hyperapp provides fragmented state and actions to prevent any collision
const actions = {
  handleClick: (state, actions, i) => {
    const history = state.history.slice(0, state.stepNumber + 1);
    const current = history[history.length - 1];
    const squares = current.squares.slice();
    if (calculateWinner(squares) || squares[i]) {
      return;
    }
    squares[i] = state.xIsNext ? "X" : "O";
    return {
      history: history.concat([
        {
          squares: squares
        }
      ]),
      stepNumber: history.length,
      xIsNext: !state.xIsNext
    };
  },
  jumpTo: (state, actions, step) => {
    return {
      stepNumber: step,
      xIsNext: step % 2 === 0
    };
  }
};

//A central "view" function
const view = (state, actions) => <Game state={state} actions={actions} />;

// ========================================

app({ state, actions, view });

const calculateWinner = squares => {
  const lines = [
    [0, 1, 2],
    [3, 4, 5],
    [6, 7, 8],
    [0, 3, 6],
    [1, 4, 7],
    [2, 5, 8],
    [0, 4, 8],
    [2, 4, 6]
  ];
  for (let i = 0; i < lines.length; i++) {
    const [a, b, c] = lines[i];
    if (squares[a] && squares[a] === squares[b] && squares[a] === squares[c]) {
      return squares[a];
    }
  }
  return null;
};