Calculate the sum of object values in JavaScript when all other values in the object are identical

Question

Calculate the sum of object values in JavaScript when all other values in the object are identical

Recently, I've been delving into JS high array methods and encountered an array of objects featuring cost categories and values:

[{category: "Bars", amount: 31231},
{category: "Transport", amount: 1297},
{category: "Utilities", amount: 12300},
{category: "Bars", amount: 2000},
{category: "Transport", amount: 2500},
{category: "Education", amount: 21321}]

My aim is to condense this array by summing the 'amount' values as follows:

[{category: "Bars", amount: 33231},  //31231+2000
{category: "Transport", amount: 3797}, //1297+2500
{category: "Utilities", amount: 12300},
{category: "Education", amount: 21321}]

I attempted using reduce() and forEach(), but have not yet found a solution to resolve the issue. Appreciate any guidance!

javascript arrays

Answer 1

Answer №1

To achieve this, utilize the `reduce` method which allows you to iterate over the array items. For each item, check if the category does not exist in the `newObject`. If it doesn't, initialize it with a value of 0 and then add up the amounts.

var objects = [{category: "Bars", amount: 31231},
{category: "Transport", amount: 1297},
{category: "Utilities", amount: 12300},
{category: "Bars", amount: 2000},
{category: "Transport", amount: 2500},
{category: "Education", amount: 21321}];

var newObjectsMerged = objects.reduce((object, item) => {
  var category = item.category;
  var amount = item.amount;
  if (!object.hasOwnProperty(category)) {
    object[category] = 0;
  }
  
  object[category] += amount;
  return object;
}, {});

console.log("newObjectsMerged", newObjectsMerged);

Answer 2

To achieve this, utilize the `reduce` method which allows you to iterate over the array items. For each item, check if the category does not exist in the `newObject`. If it doesn't, initialize it with a value of 0 and then add up the amounts.

var objects = [{category: "Bars", amount: 31231},
{category: "Transport", amount: 1297},
{category: "Utilities", amount: 12300},
{category: "Bars", amount: 2000},
{category: "Transport", amount: 2500},
{category: "Education", amount: 21321}];

var newObjectsMerged = objects.reduce((object, item) => {
  var category = item.category;
  var amount = item.amount;
  if (!object.hasOwnProperty(category)) {
    object[category] = 0;
  }
  
  object[category] += amount;
  return object;
}, {});

console.log("newObjectsMerged", newObjectsMerged);

Answer 3

Answer №2

To simplify the array, you can utilize finc to manipulate the object and either update it or add a new array to the final result.

var exampleArray = [{ category: "Bars", amount: 31231 }, { category: "Transport", amount: 1297 }, { category: "Utilities", amount: 12300 }, { category: "Bars", amount: 2000 }, { category: "Transport", amount: 2500 }, { category: "Education", amount: 21321 }],
    result = exampleArray.reduce((r, { category, amount }) => {
        var temp = r.find(o => o.category === category);
        if (temp) {
            temp.amount += amount;
        } else {
            r.push({ category, amount });
        }
        return r;
    }, []);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 4

To simplify the array, you can utilize finc to manipulate the object and either update it or add a new array to the final result.

var exampleArray = [{ category: "Bars", amount: 31231 }, { category: "Transport", amount: 1297 }, { category: "Utilities", amount: 12300 }, { category: "Bars", amount: 2000 }, { category: "Transport", amount: 2500 }, { category: "Education", amount: 21321 }],
    result = exampleArray.reduce((r, { category, amount }) => {
        var temp = r.find(o => o.category === category);
        if (temp) {
            temp.amount += amount;
        } else {
            r.push({ category, amount });
        }
        return r;
    }, []);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 5

Answer №3

let expenses = [{category: "Food", amount: 500},
{category: "Transportation", amount: 100},
{category: "Utilities", amount: 200},
{category: "Food", amount: 150},
{category: "Transportation", amount: 75},
{category: "Entertainment", amount: 300}];


let totalExpensesByCategory = expenses.reduce(function (accumulator, expense) {
  
  let summarizedExpense = accumulator.get(expense.category);
  if (!summarizedExpense) {
    summarizedExpense = expense;
  } else {
    summarizedExpense.amount += expense.amount;
  }
  
  accumulator.set(expense.category, summarizedExpense);
  
  return accumulator;
}, new Map());

console.log(Array.from(totalExpensesByCategory.values()))

Answer 6

let expenses = [{category: "Food", amount: 500},
{category: "Transportation", amount: 100},
{category: "Utilities", amount: 200},
{category: "Food", amount: 150},
{category: "Transportation", amount: 75},
{category: "Entertainment", amount: 300}];


let totalExpensesByCategory = expenses.reduce(function (accumulator, expense) {
  
  let summarizedExpense = accumulator.get(expense.category);
  if (!summarizedExpense) {
    summarizedExpense = expense;
  } else {
    summarizedExpense.amount += expense.amount;
  }
  
  accumulator.set(expense.category, summarizedExpense);
  
  return accumulator;
}, new Map());

console.log(Array.from(totalExpensesByCategory.values()))

Answer 7

Answer №4

Give this a shot:

let expenses = [{category: "Groceries", amount: 200},
{category: "Transportation", amount: 50},
{category: "Utilities", amount: 120},
{category: "Groceries", amount: 100},
{category: "Entertainment", amount: 75}];

// extract unique categories
let categories = [...new Set(expenses.map(item => item.category))];

// calculate total expenses for each category
let result = categories.map(category => {
    return {
        category: category,
        totalAmount: expenses.filter(item => item.category === category).reduce((acc, curr) => acc + curr.amount, 0)
    };
});

Answer 8

Give this a shot:

let expenses = [{category: "Groceries", amount: 200},
{category: "Transportation", amount: 50},
{category: "Utilities", amount: 120},
{category: "Groceries", amount: 100},
{category: "Entertainment", amount: 75}];

// extract unique categories
let categories = [...new Set(expenses.map(item => item.category))];

// calculate total expenses for each category
let result = categories.map(category => {
    return {
        category: category,
        totalAmount: expenses.filter(item => item.category === category).reduce((acc, curr) => acc + curr.amount, 0)
    };
});

Answer 9

Answer №5

An ES6 solution using Array.prototype.reduce and Object.keys:

const data = [{category: "Bars", amount: 31231},{category: "Transport", amount: 1297},{category: "Utilities", amount: 12300},{category: "Bars", amount: 2000},{category: "Transport", amount: 2500},{category: "Education", amount: 21321}];

const grouped = data.reduce((all, {category: c, amount: a}) =>
    ({...all, [c]: (all[c] || 0) + a }), {});

const result = Object.keys(grouped).map(k => ({category: k,amount: grouped[k] }));

console.log(result);

Answer 10

An ES6 solution using Array.prototype.reduce and Object.keys:

const data = [{category: "Bars", amount: 31231},{category: "Transport", amount: 1297},{category: "Utilities", amount: 12300},{category: "Bars", amount: 2000},{category: "Transport", amount: 2500},{category: "Education", amount: 21321}];

const grouped = data.reduce((all, {category: c, amount: a}) =>
    ({...all, [c]: (all[c] || 0) + a }), {});

const result = Object.keys(grouped).map(k => ({category: k,amount: grouped[k] }));

console.log(result);

Calculate the sum of object values in JavaScript when all other values in the object are identical

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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