Using values from a preexisting array to generate new arrays in JavaScript

Question

Using values from a preexisting array to generate new arrays in JavaScript

I'm currently facing a challenge in JavaScript where I need to generate arrays based on the values of another array.

For instance, I have an array of dates in string format (dates) listed below:

["30/09/2015", "31/10/2015", "30/11/2015", "31/12/2015"]

Additionally, I have an Object that represents various bank accounts (balancesSortByAccId) as shown:

Cash - (Array size: 3)
id: 1, date: "30/09/2015", balance: 30
id: 2, date: "31/10/2015", balance: 50
id: 3, date: "30/11/2015", balance: 100

Natwest - (Array size: 2)
id: 4, date: "30/11/2015", balance: 400
id: 5, date: "31/12/2015", balance: 200

My goal is to create arrays for each date in the 'dates' array by retrieving balances from the accounts in 'balancesSortByAccId'. Here's what I aim to achieve:

[30, 50, 100, null]
[null, null, 400, 200]

If you have any suggestions on how I could accomplish this, please let me know!

UPDATE: You can view my jsfiddle code here - https://jsfiddle.net/gx8bLehb/

javascript arrays sorting

Answer 1

Answer №1

To streamline the process, consider organizing your `cash` and `natwest` arrays into a sorted hash based on date, like renaming it to `balancesByDate`:

var balancesByDate = _.groupBy(cash, function(entry) {return entry.date});

Then, utilize an array's `map()` method, such as one from lodash, to loop through the `dates` array. For each date, search for the account line in the `balancesByDate` hash. Return the `balance` property using the `map` method.

dates.forEach(function(date){
  if (balancesByDate[date]) {
    results.push(_.map(balancesByDate[date], function(line){
       return line.balance;
    }));
  } else {
    results.push(null);
  }
});

It's important to note that your data set might have duplicate balances for a day. Consider this factor while planning (my code returns an array for each day).

https://jsfiddle.net/hdpuuc5d/1/

Answer 2

To streamline the process, consider organizing your `cash` and `natwest` arrays into a sorted hash based on date, like renaming it to `balancesByDate`:

var balancesByDate = _.groupBy(cash, function(entry) {return entry.date});

Then, utilize an array's `map()` method, such as one from lodash, to loop through the `dates` array. For each date, search for the account line in the `balancesByDate` hash. Return the `balance` property using the `map` method.

dates.forEach(function(date){
  if (balancesByDate[date]) {
    results.push(_.map(balancesByDate[date], function(line){
       return line.balance;
    }));
  } else {
    results.push(null);
  }
});

It's important to note that your data set might have duplicate balances for a day. Consider this factor while planning (my code returns an array for each day).

https://jsfiddle.net/hdpuuc5d/1/

Answer 3

Answer №2

An implementation using vanilla JavaScript and a date helper object:

const datesArray = ["30/09/2015", "31/10/2015", "30/11/2015", "31/12/2015"];
const datesObject = datesArray.reduce((acc, date, index) => {
  acc[date] = index; 
  return acc;
}, {});
const accountBalances = {
    Cash: [
        { id: 1, date: "30/09/2015", balance: 30 },
        { id: 2, date: "31/10/2015", balance: 50 },
        { id: 3, date: "30/11/2015", balance: 100 }
    ],
    Natwest: [
        { id: 4, date: "30/11/2015", balance: 400 },
        { id: 5, date: "31/12/2015", balance: 200 }
    ]
};
const finalResult = {};

Object.keys(accountBalances).forEach(key => {
    finalResult[key] = Array.from({ length: datesArray.length }, () => null);
    accountBalances[key].forEach(entry => {
        finalResult[key][datesObject[entry.date]] = entry.balance;
    });
});

document.write('<pre>' + JSON.stringify(finalResult, 0, 4) + '</pre>');

Answer 4

An implementation using vanilla JavaScript and a date helper object:

const datesArray = ["30/09/2015", "31/10/2015", "30/11/2015", "31/12/2015"];
const datesObject = datesArray.reduce((acc, date, index) => {
  acc[date] = index; 
  return acc;
}, {});
const accountBalances = {
    Cash: [
        { id: 1, date: "30/09/2015", balance: 30 },
        { id: 2, date: "31/10/2015", balance: 50 },
        { id: 3, date: "30/11/2015", balance: 100 }
    ],
    Natwest: [
        { id: 4, date: "30/11/2015", balance: 400 },
        { id: 5, date: "31/12/2015", balance: 200 }
    ]
};
const finalResult = {};

Object.keys(accountBalances).forEach(key => {
    finalResult[key] = Array.from({ length: datesArray.length }, () => null);
    accountBalances[key].forEach(entry => {
        finalResult[key][datesObject[entry.date]] = entry.balance;
    });
});

document.write('<pre>' + JSON.stringify(finalResult, 0, 4) + '</pre>');

Using values from a preexisting array to generate new arrays in JavaScript

Answer №1

Answer №2

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