Group long object of dates, into object of months

user_9115678 0
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I have a very long object of dates, which pairs a date with a price/number. For example:

let obj = {
"2022-09-17": 45,
"2022-09-18": 35,
"2022-09-19": 34,
"2022-09-20": 26,
"2022-09-21": 25,
"2022-09-22": 33,
"2022-09-23": 56,
"2022-09-24": 39,
"2022-09-25": 49,
"2022-09-26": 25,
"2022-09-27": 25,
"2022-09-28": 25,
"2022-09-29": 33,
"2022-09-30": 42,
"2022-10-01": 28,
"2022-10-02": 38,
"2022-10-03": 35,
"2022-10-04": 25,
"2022-10-05": 25,
"2022-10-06": 31
}

What is the best way to regroup this object as an array of months, which correlate to the dates and contain the key/values?

Eg - like this screenshot:

enter image description here

I want to group the key/value pair by months, so I can later, then loop through all months, to find the lowest price of each month.

But first, I wanted to figure out the best way to break up this object, in months?

Thanks,

object for-loop sorting arrays javascript
2 Answers

As often, reduce is a good solution here

let object = {
  "2022-09-17": 45,
  "2022-09-18": 35,
  "2022-09-19": 34,
  "2022-09-20": 26,
  "2022-09-21": 25,
  "2022-09-22": 33,
  "2022-09-23": 56,
  "2022-09-24": 39,
  "2022-09-25": 49,
  "2022-09-26": 25,
  "2022-09-27": 25,
  "2022-09-28": 25,
  "2022-09-29": 33,
  "2022-09-30": 42,
  "2022-10-01": 28,
  "2022-10-02": 38,
  "2022-10-03": 35,
  "2022-10-04": 25,
  "2022-10-05": 25,
  "2022-10-06": 31
}

const objectMonth = Object
  .keys(object)
  .reduce((acc, key) => {
    const date = new Date(key)
    const month = date.toLocaleString('default', { month: 'long' })
    acc[month] = acc[month] || []
    acc[month].push({
      date: key,
      price: object[key]
    })
    return acc
  }, {})

console.log(objectMonth)
user_61089470

You can do something like this.

Logic

  • Loop through the entries in object
  • Split the date into year, month and date.
  • Get the month name with some logic.
  • Reduce this array of entries in the object.

let obj = {
  "2022-09-17": 45,
  "2022-09-18": 35,
  "2022-09-19": 34,
  "2022-09-20": 26,
  "2022-09-21": 25,
  "2022-09-22": 33,
  "2022-09-23": 56,
  "2022-09-24": 39,
  "2022-09-25": 49,
  "2022-09-26": 25,
  "2022-09-27": 25,
  "2022-09-28": 25,
  "2022-09-29": 33,
  "2022-09-30": 42,
  "2022-10-01": 28,
  "2022-10-02": 38,
  "2022-10-03": 35,
  "2022-10-04": 25,
  "2022-10-05": 25,
  "2022-10-06": 31,
};
const months = [
  "january",
  "february",
  "march",
  "april",
  "may",
  "june",
  "july",
  "august",
  "september",
  "october",
  "november",
  "december",
];
const splittedData = Object.entries(obj).reduce(
  (acc, [dateStr, value]) => {
    const [year, month, date] = dateStr.split("-");
    if (!acc[months[+month - 1]]) {
      acc[months[+month - 1]] = [];
    }
    acc[months[+month - 1]].push({ [dateStr]: value });
    return acc;
  },
  {}
);
console.log(splittedData);

user_60993270
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