每次更新 state 時都會調用隨機播放 function 嗎？

Question

問題很簡單，我有一個洗牌 function 洗牌數組，數字呈現為一副牌中的牌，應用程序很簡單，當點擊兩張相同號碼的牌時，它們需要相同的顏色。

所以我創建了一個 state 這是一個數組，它只接收兩張卡進行比較，一旦比較完成，數組長度返回 0 然后再次推送兩張卡，依此類推。

現在問題是洗牌 function 每次更新 state 時都會一次又一次地工作，這使得卡片每次都用不同的數字重新渲染（洗牌）

代碼：

  const icons = [1, 2, 3, 4, 1, 2, 3, 4, 5, 6, 7, 8, 5, 6, 7, 8];

  const shuffle = (cards) => {
    let counter = cards.length;

    // While there are elements in the array
    while (counter > 0) {
      // Pick a random index
      let index = Math.floor(Math.random() * counter);

      // Decrease counter by 1
      counter--;

      // And swap the last element with it
      let temp = cards[counter];
      cards[counter] = cards[index];
      cards[index] = temp;
    }

    return cards;
  }

  const shuffledCards = shuffle(icons);

  const [cards, setCards] = useState([]);
  const [isCorrect, checkCorrect] = useState(false)

  const addCard = (card) => {
    if (cards.length < 2) {
      setCards([...cards, card]);
    }

    if(cards.length === 2) {
      compareCards(cards);
      setCards([]);
     }
  }

  const compareCards = (cards) => {
    if(cards[0] === cards[1] ) {
      checkCorrect(true);
    }
  } 

   return (
    <div className="App">
      <Game shuffledCards={shuffledCards} addCard={addCard} />
    </div>
  );
}

const Game = (props) => {

    const { shuffledCards, addCard } = props;

    return (
        <div className="game">
            <div className="deck">
                {
                    shuffledCards.map((c, i) => {
                        return (
                            <div className="card" key={i} onClick={() => addCard(c)}>{c}</div>
                        );
                    })
                }
            </div>

        </div>
    )
}


export default App;

Answer 1

你可以使用useEffect：

const [cards, setCards] = useState([]);
useEffect(()=>{shuffle()},[cards])