JavaScript code that compares dates in an array, then calculates the total price for each month and year

Question

JavaScript code that compares dates in an array, then calculates the total price for each month and year

I have a JSON file containing various transactions with both a date and a price attribute. My goal is to compare the dates, identify transactions that occur in the same month and year, and calculate the total price of those transactions.

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 ...
  }
};

Although I attempted to iterate through the JSON object, I am currently struggling to devise a method for comparing the dates effectively.

javascript arrays json sorting date

Answer 1

Answer №1

Note: Updated example using Object.assign instead of Object spread.

To calculate the total sum of prices, you will need to utilize the reduce method. Refer to the comments for more information.

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) => {
    // Obtain the current date object
    const date = new Date(current.date);
    // Create a key/identifier
    const key = `${date.getFullYear()}-${date.getMonth() + 1}`;
    // Retrieve the previous price from the accumulator
    const previousPrice = acc[key]; 
    // Set up the current price value and ensure it is treated as a number.
    let currentPrice = Number(current.price);
    // If there was a previous value (not undefined)
    if (previousPrice) {
      // Add it to our current value
      currentPrice += Number(previousPrice);
    }
    // Return the updated accumulator value
    return Object.assign(acc, {
      [key]: currentPrice, 
    })
  }, {})

  // Once all values are calculated, extract dates and sort them in ascending order.
  // Create an array with each value from the summed object in sortedArray
  const sortedArray = Object.keys(summed).sort().map((val) => {
    return summed[val];
  });

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

sumTransactions(transactions);

Answer 2

Note: Updated example using Object.assign instead of Object spread.

To calculate the total sum of prices, you will need to utilize the reduce method. Refer to the comments for more information.

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) => {
    // Obtain the current date object
    const date = new Date(current.date);
    // Create a key/identifier
    const key = `${date.getFullYear()}-${date.getMonth() + 1}`;
    // Retrieve the previous price from the accumulator
    const previousPrice = acc[key]; 
    // Set up the current price value and ensure it is treated as a number.
    let currentPrice = Number(current.price);
    // If there was a previous value (not undefined)
    if (previousPrice) {
      // Add it to our current value
      currentPrice += Number(previousPrice);
    }
    // Return the updated accumulator value
    return Object.assign(acc, {
      [key]: currentPrice, 
    })
  }, {})

  // Once all values are calculated, extract dates and sort them in ascending order.
  // Create an array with each value from the summed object in sortedArray
  const sortedArray = Object.keys(summed).sort().map((val) => {
    return summed[val];
  });

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

sumTransactions(transactions);

Answer 3

Answer №2

After some experimentation, I managed to find a solution that works:

var transactions = [
    {
        date: "2017-11-17",
        price: "28",
    },
    {
        date: "2017-12-17",
        price: "22",
    },
    {
        date: "2017-12-17",
        price: "20",
    }
]

var sumedUpDates = [];
var prices = [];

function isDateSumedUp(date) {
    return sumedUpDates.indexOf(date.substring(0, 7)) !== -1;
}

function sumUpDate(date) {
    var sum = 0;

    transactions.forEach(t => {
        if(t.date.substring(0, 7) === date.substring(0, 7)) {
            sum += parseInt(t.price);
        }
    });

    sumedUpDates.push(date.substring(0, 7));
    prices.push(sum);
}

transactions.forEach(t => {
    if(!isDateSumedUp(t.date)) {
        sumUpDate(t.date);
    }
});

var obj = {};

sumedUpDates.forEach((d, i) => obj[d] = prices[i]);

console.log(obj);

Answer 4

After some experimentation, I managed to find a solution that works:

var transactions = [
    {
        date: "2017-11-17",
        price: "28",
    },
    {
        date: "2017-12-17",
        price: "22",
    },
    {
        date: "2017-12-17",
        price: "20",
    }
]

var sumedUpDates = [];
var prices = [];

function isDateSumedUp(date) {
    return sumedUpDates.indexOf(date.substring(0, 7)) !== -1;
}

function sumUpDate(date) {
    var sum = 0;

    transactions.forEach(t => {
        if(t.date.substring(0, 7) === date.substring(0, 7)) {
            sum += parseInt(t.price);
        }
    });

    sumedUpDates.push(date.substring(0, 7));
    prices.push(sum);
}

transactions.forEach(t => {
    if(!isDateSumedUp(t.date)) {
        sumUpDate(t.date);
    }
});

var obj = {};

sumedUpDates.forEach((d, i) => obj[d] = prices[i]);

console.log(obj);

Answer 5

Answer №3

This method utilizes the map function to convert dates in each object entry into a year/month format, and then uses the reduce function to sum them based on those separated dates.

const transactions = [
  {date:"2017-11-17", price: "28",}, 
  {date:"2017-12-17", price: "28",}, 
  {date:"2017-11-17", price: "20",},
  {date:"2017-12-17", price: "2",}, 
  {date:"2017-11-17", price: "58",}, 
  {date:"2017-11-17", price: "8",}, 
  {date:"2017-10-17", price: "30",}, 
  {date:"2018-11-17", price: "1",},
];

const mapper = single => {
  let d = single.date.split('-');
  let p = Number(single.price);
  return { year: d[0], month: d[1], price: p };
}

const reducer = (group, current) => {
  let i = group.findIndex(single => (single.year == current.year && single.month == current.month));
  if (i == -1) {
    return [ ...group, current ];
  }

  group[i].price += current.price;
  return group;
};

const totalPricesByDate = transactions.map(mapper).reduce(reducer, []);
console.log(totalPricesByDate);

Answer 6

This method utilizes the map function to convert dates in each object entry into a year/month format, and then uses the reduce function to sum them based on those separated dates.

const transactions = [
  {date:"2017-11-17", price: "28",}, 
  {date:"2017-12-17", price: "28",}, 
  {date:"2017-11-17", price: "20",},
  {date:"2017-12-17", price: "2",}, 
  {date:"2017-11-17", price: "58",}, 
  {date:"2017-11-17", price: "8",}, 
  {date:"2017-10-17", price: "30",}, 
  {date:"2018-11-17", price: "1",},
];

const mapper = single => {
  let d = single.date.split('-');
  let p = Number(single.price);
  return { year: d[0], month: d[1], price: p };
}

const reducer = (group, current) => {
  let i = group.findIndex(single => (single.year == current.year && single.month == current.month));
  if (i == -1) {
    return [ ...group, current ];
  }

  group[i].price += current.price;
  return group;
};

const totalPricesByDate = transactions.map(mapper).reduce(reducer, []);
console.log(totalPricesByDate);

Answer 7

Answer №4

let data = [];
for (let i = 0; i < transactions.length; i++) {
    let date = new Date(transactions[i].date);
    let ym = date.getFullYear() + "-" + date.getMonth();
    if (data[ym] == null) {
        data[ym] = 0;
    }
    data[ym] += parseInt(transactions[i].price);
}

Using the provided information

let transactions = [{
                date: "2017-11-17",
                price: "28",
            },
            {
                date: "2017-12-17",
                price: "5",
            },
            {
                date: "2016-02-17",
                price: "28",
            },
            {
                date: "2015-11-17",
                price: "25",
            },
            {
                date: "2016-02-17",
                price: "12",
            },
            {
                date: "2017-11-17",
                price: "50",
            }
        ];

This code will sum up all duplicates of year-months like this :

[
    2017-10: 78, 
    2017-11: 5, 
    2016-1: 40, 
    2015-10: 25
]

Answer 8

let data = [];
for (let i = 0; i < transactions.length; i++) {
    let date = new Date(transactions[i].date);
    let ym = date.getFullYear() + "-" + date.getMonth();
    if (data[ym] == null) {
        data[ym] = 0;
    }
    data[ym] += parseInt(transactions[i].price);
}

Using the provided information

let transactions = [{
                date: "2017-11-17",
                price: "28",
            },
            {
                date: "2017-12-17",
                price: "5",
            },
            {
                date: "2016-02-17",
                price: "28",
            },
            {
                date: "2015-11-17",
                price: "25",
            },
            {
                date: "2016-02-17",
                price: "12",
            },
            {
                date: "2017-11-17",
                price: "50",
            }
        ];

This code will sum up all duplicates of year-months like this :

[
    2017-10: 78, 
    2017-11: 5, 
    2016-1: 40, 
    2015-10: 25
]

Answer 9

Answer №5

One alternative approach is to use the reduce method:

const transactions = [
  {date: "2020-05-15", price: "35"},
  {date: "2020-06-20', price: "50"},
  {date: "2020-06-30", price: "45"}
];

const result = transactions.reduce((acc, obj) => {
  const key = obj.date.substr(0,7);
  acc[key] = (acc[key] || 0) + +obj.price;
  return acc;
}, Object.create(null));

console.log(result);

Answer 10

One alternative approach is to use the reduce method:

const transactions = [
  {date: "2020-05-15", price: "35"},
  {date: "2020-06-20', price: "50"},
  {date: "2020-06-30", price: "45"}
];

const result = transactions.reduce((acc, obj) => {
  const key = obj.date.substr(0,7);
  acc[key] = (acc[key] || 0) + +obj.price;
  return acc;
}, Object.create(null));

console.log(result);

JavaScript code that compares dates in an array, then calculates the total price for each month and year

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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