JavaScript:比较数组中的日期并对每个月/年的 "price"求和

Question

我有一个包含多个 transactions 的 json 文件，其中包含一个 date 和一个 price 属性。现在我想比较日期，如果它们在同一年和同一年，我想总结价格。

JSON:

transactions: [
{
  date: "2017-11-17",
  price: "28",
},
{
  ...
}

JavaScript:

request.onload = function() {
  for(const transaction of request.response.transactions) {
    let year = new Date(transaction.date).getFullYear();
    let month = new Date(transaction.date).getMonth();

    console.log(year + ' ' + month);  // output: 2017-11 ...
  }
};

我试图遍历 json 对象，但我很难找到比较日期的解决方案。

Answer 1

编辑:使用 Object.assign 而不是 Object spread 编辑示例。

您需要使用reduce 来对价格求和。有关详细信息，请参阅评论。

const transactions = [{
    date: "2017-11-17",
    price: "28",
  },
  {
    date: "2017-12-17",
    price: "23",
  },
  {
    date: "2017-11-17",
    price: "12",
  },
  {
    date: "2017-10-17",
    price: "55",
  },
  {
    date: "2017-11-17",
    price: "09",
  },
];

const sumTransactions = (transactions) => {

  const summed = transactions.reduce((acc, current) => {
    // Get the current date object
    const date = new Date(current.date);
    // Create your key/identifier
    const key = `${date.getFullYear()}-${date.getMonth() + 1}`;
    // Retreive the previous price from the accumulator
    const previousPrice = acc[key]; // Might also return undefined
    // Create your temp current price value, and be sure to deal with numbers.
    let currentPrice = Number(current.price);
    // If you had a previous value (and not undefined)
    if (previousPrice) {
      // Add it to our value
      currentPrice += Number(previousPrice);
    }
    // Return the future accumulator value
    return Object.assign(acc, {
      [key]: currentPrice, // new values will overwrite same old values
    })
  }, {})

  // Once we have all values, get the dates, and sort them (default: earlier first)
  // Return an array of each value from the summed object to our sortedArray
  const sortedArray = Object.keys(summed).sort().map((val) => {
    return summed[val];
  });

  console.log("sortedArray", sortedArray);
};

sumTransactions(transactions);