What is the best way to deduct specific values from two arrays of objects?

Question

What is the best way to deduct specific values from two arrays of objects?

Here I am, being a little silly by posing a not-so-simple question that has been nagging me for quite some time. Let's dive into the data:


    const demo1 = [
       { count: 156, monthCount: 1, year: 2018 },
       {  count: 165, monthCount: 2, year: 2018 },
       {  count: 103, monthCount: 3, year: 2018 },
       {  count: 60, monthCount: 4, year: 2018 }
    ]
    const data2 = [
      { count: 100, monthCount: 1, year: 2019 },
      {  count: 55, monthCount: 2, year: 2019 },
      {  count: 99, monthCount: 3, year: 2019 },
      {  count: 130, monthCount: 4, year: 2019 }
    ]

My quest is to acquire data3 which equals data2 - data1, with key attributes. The expected output should look something like this:

[
    {count: 56, monthCount: 1 },
    {count: 100, monthCount: 2 },
    {count: 60, monthCount: 3 },
    {count: 70, monthCount: 4 }
]

javascript arrays

Answer 1

Answer №1

To achieve the subtraction of data2 - data1, you can utilize vanilla JavaScript for this operation. Here is an illustration along with your provided data:

const data1 = [
  { count: 156, monthCount: 1, year: 2018 },
  { count: 165, monthCount: 2, year: 2018 },
  { count: 103, monthCount: 3, year: 2018 },
  { count: 60, monthCount: 4, year: 2018 }
];
const data2 = [
 { count: 100, monthCount: 1, year: 2019 },
 { count: 55, monthCount: 2, year: 2019 },
 { count: 99, monthCount: 3, year: 2019 },
 { count: 130, monthCount: 4, year: 2019 }
];

Here is an example:

const combined = data1.concat(data2);
console.log(`combined, not calculated`, combined);

const desired = [...combined.reduce((r, {monthCount, count}) => {
const key = monthCount;

  const item = r.get(key) || Object.assign({}, {
    count: 0,
    monthCount: monthCount
  });

  if (item.count === 0)
    item.count = -count;
  else
    item.count += +count;

  return r.set(key, item);
}, new Map).values()];

console.log(`desired: `, desired)

OUTPUT:

[
    {count: -56, monthCount: 1},
    {count: -110, monthCount: 2},
    {count: -4, monthCount: 3},
    {count: 70, monthCount: 4},
]

Answer 2

To achieve the subtraction of data2 - data1, you can utilize vanilla JavaScript for this operation. Here is an illustration along with your provided data:

const data1 = [
  { count: 156, monthCount: 1, year: 2018 },
  { count: 165, monthCount: 2, year: 2018 },
  { count: 103, monthCount: 3, year: 2018 },
  { count: 60, monthCount: 4, year: 2018 }
];
const data2 = [
 { count: 100, monthCount: 1, year: 2019 },
 { count: 55, monthCount: 2, year: 2019 },
 { count: 99, monthCount: 3, year: 2019 },
 { count: 130, monthCount: 4, year: 2019 }
];

Here is an example:

const combined = data1.concat(data2);
console.log(`combined, not calculated`, combined);

const desired = [...combined.reduce((r, {monthCount, count}) => {
const key = monthCount;

  const item = r.get(key) || Object.assign({}, {
    count: 0,
    monthCount: monthCount
  });

  if (item.count === 0)
    item.count = -count;
  else
    item.count += +count;

  return r.set(key, item);
}, new Map).values()];

console.log(`desired: `, desired)

OUTPUT:

[
    {count: -56, monthCount: 1},
    {count: -110, monthCount: 2},
    {count: -4, monthCount: 3},
    {count: 70, monthCount: 4},
]

Answer 3

Answer №2

const data1 = [
       { count: 156, monthCount: 1, year: 2018 },
       {  count: 165, monthCount: 2, year: 2018 },
       {  count: 103, monthCount: 3, year: 2018 },
       {  count: 60, monthCount: 4, year: 2018 }
    ]
  const data2 = [
    { count: 100, monthCount: 1, year: 2019 },
    {  count: 55, monthCount: 2, year: 2019 },
    {  count: 99, monthCount: 3, year: 2019 },
    {  count: 130, monthCount: 4, year: 2019 }
  ];

const subtractData = (arrOne, arrTwo) => {
  const newArr = []
  arrOne.forEach((elOne) => {
    arrTwo.forEach((elTwo) => {
      if(elOne.monthCount === elTwo.monthCount){
        const count = Math.abs(Number(elOne.count) - Number(elTwo.count));
        const newObj = {
         ...elOne,
         count
        }
        delete newObj.year;
        newArr.push(newObj)
      }
    })
  })

  return newArr;
}

console.log(subtractData(data1, data2))

Answer 4

const data1 = [
       { count: 156, monthCount: 1, year: 2018 },
       {  count: 165, monthCount: 2, year: 2018 },
       {  count: 103, monthCount: 3, year: 2018 },
       {  count: 60, monthCount: 4, year: 2018 }
    ]
  const data2 = [
    { count: 100, monthCount: 1, year: 2019 },
    {  count: 55, monthCount: 2, year: 2019 },
    {  count: 99, monthCount: 3, year: 2019 },
    {  count: 130, monthCount: 4, year: 2019 }
  ];

const subtractData = (arrOne, arrTwo) => {
  const newArr = []
  arrOne.forEach((elOne) => {
    arrTwo.forEach((elTwo) => {
      if(elOne.monthCount === elTwo.monthCount){
        const count = Math.abs(Number(elOne.count) - Number(elTwo.count));
        const newObj = {
         ...elOne,
         count
        }
        delete newObj.year;
        newArr.push(newObj)
      }
    })
  })

  return newArr;
}

console.log(subtractData(data1, data2))

What is the best way to deduct specific values from two arrays of objects?

Answer №1

Answer №2

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