如何在 Java Script 中计算 Plaid API 事务数组的值的总和？

Question

对于这个可能很愚蠢的问题，我深表歉意——我对编码/JavaScript 还很陌生。

我正在使用Plaid's 沙盒环境在沙盒环境中提取事务数据。现在，我将以下内容定义为 transactionData：

    let transactionsData = [];
transactions.forEach(function(account) {
  account.transactions.forEach(function(transaction) {
    transactionsData.push({
      account: account.accountName,
      date: transaction.date,
      category: transaction.category[0],
      name: transaction.name,
      amount: transaction.amount
    });
  });
});

我可以像这样成功地在material table 中逐行呈现单个交易：

    const transactionsColumns = [
  { title: "Account", field: "account" },
  { title: "Date", field: "date", type: "date", defaultSort: "desc" },
  { title: "Name", field: "name" },
  { title: "Amount", field: "amount", type: "numeric" },
  { title: "Category", field: "category" }
];

          <MaterialTable
            columns={transactionsColumns}
            data={transactionsData}
            }}

我知道这必须非常简单，但我要做的就是对 transactionsData 求和，然后在我页面的其他地方呈现单个求和值。如果我写 transactionsData.length 我可以很容易地收到交易的数量。我尝试了以下有点相似的语法，但没有发现它可以工作：

array.reduce(function(total, currentValue, currentIndex, arr), initialValue)

任何帮助将不胜感激。

Answer 1

这是总数，使用Array.prototype.reduce：

const transformed = [{"account":"Navy Federal Credit Union","date":"2020-01-01","category":"Travel","name":"United Airlines","amount":500},{"account":"Navy Federal Credit Union","date":"2019-12-30","category":"Travel","name":"Uber 072515 SF**POOL**","amount":6.33},{"account":"Navy Federal Credit Union","date":"2019-12-27","category":"Food and Drink","name":"Tectra Inc","amount":500}]

const unrounded = transformed.reduce(
  (acc, { amount }) => acc + amount,
  0
);

const roundCents = amount => Math.round(amount * 100) / 100;

const total = roundCents(unrounded);

console.log(total);

上面的一个更简单的版本，没有解构：

const transformed = [{"account":"Navy Federal Credit Union","date":"2020-01-01","category":"Travel","name":"United Airlines","amount":500},{"account":"Navy Federal Credit Union","date":"2019-12-30","category":"Travel","name":"Uber 072515 SF**POOL**","amount":6.33},{"account":"Navy Federal Credit Union","date":"2019-12-27","category":"Food and Drink","name":"Tectra Inc","amount":500}]

const unrounded = transformed.reduce(
  (acc, transaction) => acc + transaction.amount,
  0
);

const roundCents = amount => Math.round(amount * 100) / 100;

const total = roundCents(unrounded);

console.log(total);

下面是如何将transactionsData 转换为Array.prototype.flatMap 和Array.prototype.map，而不是forEach：

const transactionsData = [{ accountName: 'a1', transactions: [{ date: '2020', category: ['c1'], name: 'n1', amount: 100 }, { date: '2020', category: ['c2'], name: 'n2', amount: 100 }]}, { accountName: 'a2', transactions: [{ date: '2020', category: ['c3'], name: 'n3', amount: 100 }, { date: '2020', category: ['c4'], name: 'n4', amount: 100 }]}]

const transformed = transactionsData.flatMap(({ accountName, transactions }) =>
  transactions.map(({ date, category, name, amount }) => ({
      account: accountName,
      date,
      category: category[0],
      name,
      amount
    })
  )
);

console.log(transformed)

再一次，一个更简单的版本，没有解构：

const transactionsData = [{ accountName: 'a1', transactions: [{ date: '2020', category: ['c1'], name: 'n1', amount: 100 }, { date: '2020', category: ['c2'], name: 'n2', amount: 100 }]}, { accountName: 'a2', transactions: [{ date: '2020', category: ['c3'], name: 'n3', amount: 100 }, { date: '2020', category: ['c4'], name: 'n4', amount: 100 }]}]

const transformed = transactionsData.flatMap(account =>
  account.transactions.map(transaction => ({
      account: account.accountName,
      date: transaction.date,
      category: transaction.category[0],
      name: transaction.name,
      amount: transaction.amount
    })
  )
);

console.log(transformed)

Array.prototype.map 是从现有数组创建新数组时使用的正确方法，Array.prototype.flatMap 是在需要扁平数组时使用的正确方法，map 会生成嵌套数组.