说明没有正确计算数字 - 只是将它们串在一起答案

【问题标题】：State not calculating numbers correctly - just stringing them together说明没有正确计算数字 - 只是将它们串在一起
【发布时间】：2023-02-11 19:10:25
【问题描述】：

所以我觉得自己像个白痴。我将数字串在一起而不是从我的州添加。我似乎无法使用正常的更新状态方法来解决它。它用于选择从库存中购买多少物品的组件。当我可以选择一次购买一个时，一切正常。现在我已经添加了应该控制它的“puchaseAmount”状态。如果我尝试一次购买 10 个，数量会中断并串成“010101010”。同样的事情也发生在拥有的物品总数上。我觉得我错过了一些简单而愚蠢的东西哈哈

  const [quantityOwned, setQuantityOwned] = useState(0);  
const [purchaseAmount, setPurchaseAmount] = useState(10);

const productIndex = newArray.findIndex((p) => p.id === product.id);

  if (productIndex !== -1) {
    newArray[productIndex].quantity = newArray[productIndex].quantity +  purchaseAmount
    const newCost = newArray[productIndex].cost * increaseConstant;
    newArray.push({
      ...product,
      cost: newCost
    });
  } else {
    newArray.push({
      ...product,
      quantity: purchaseAmount,
    });
  }

  if (productType === 'items') {
    setPlayerCharacter({
      ...playerCharacter,
      items: newArray,
    });
  }

  // // Increase product cost
  const newCost = product.cost * 1.1;
  product.cost = newCost.toFixed(2);

  // PPC Product
  if (product.type === 'pointsPerClick') {
    // Assign current values

    let currentPointsPerClick = playerCharacter.pointsPerClick;
    let currentTotalScore = playerCharacter.totalScore;

    let newPointsPerClickValue = currentPointsPerClick + product.effect;
    let newTotalScore = currentTotalScore - product.cost;

    setQuantityOwned(quantityOwned + purchaseAmount); // This is the trouble
    // i tried also (prev => prev + purchaseAmount)

    let newTotalBuildingsOwned = playerCharacter.totalBuildingsOwned;
    let newTotalItemsOwned = playerCharacter.totalItemsOwned;

    if (productType === 'items') {
      const newNum = playerCharacter.totalItemsOwned + purchaseAmount;
      newTotalItemsOwned = newNum;
    }

    if (productType === 'buildings') {
      const newNum =
        playerCharacter.newTotalBuildingsOwned + purchaseAmount;
      newTotalBuildingsOwned = newNum;
    }

    setPlayerCharacter({
      ...playerCharacter,
      pointsPerClick: newPointsPerClickValue,
      totalScore: newTotalScore,
      totalItemsOwned: newTotalItemsOwned,
      totalBuildingsOwned: newTotalBuildingsOwned,
    });
  }

【问题讨论】：

与整个组件一起共享输出。

标签： javascript reactjs state

【解决方案1】：

您将 purchaseAmount（这是一个 string）与当前值 quantityOwned/totalItemsOwned/totalBuildingsOwned（这是一个number）连接起来，得到一个 string。

在计算中使用之前，您需要使用Number() 或parseInt() 将purchaseAmount 转换为number。

setQuantityOwned(prev => prev + Number(purchaseAmount));

【讨论】：