如何计算 Java Script 中 Plaid API 事务数组的总和？

Question

为这个可能很愚蠢的问题道歉 - 我对编码/JavaScript 还很陌生。

我正在使用Plaid 的沙箱环境在沙箱环境中提取交易数据。 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
    });
  });
});

我可以成功地在材料表中逐行呈现单个事务，如下所示：

    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，但我想要做的就是对交易数据求和并在我页面的其他地方呈现该单个求和值。 如果我写 transactionsData.length，我可以很容易地收到交易的计数。 我尝试了以下有些类似的语法，但没有发现它起作用：

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

任何帮助将非常感激。

Answer 1

总共使用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);

以下是如何使用Array.prototype.flatMap和Array.prototype.map而不是forEach来转换transactionsData ：

 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，如果你想从现有的创建一个新的阵列使用正确的方法，并Array.prototype.flatMap是正确的方法来使用，如果你需要一个扁平阵列和map会生成一个嵌套的一个。