Loop through array of objects and group/increment object values on shared property value

Question

I am trying to think of the best way of looping through this array of data objects and if the wineRegion name appears more than once, I want the output array to hold this value once with the totalPrice value incremented to the value of all the matching objects totalPrice.

Here is my data array:

const data = [
  {
    wineName: 'Château Pape-Clément',
    wineRegion: 'Bordeaux (Red)',
    unitSize: '12x75cl',
    wineVintage: 2010,
    qty: 1,
    totalPrice: 1650,
  },
  {
    wineName: 'Château Beauséjour Duffau-Lagarrosse',
    wineRegion: 'Bordeaux (Red)',
    unitSize: '6x75cl',
    wineVintage: 2010,
    qty: 1,
    totalPrice: 1400,
  },
  {
    wineName: 'Vosne-Romanée, Berthaut',
    wineRegion: 'Burgundy (Red)',
    unitSize: '12x75cl',
    wineVintage: 2017,
    qty: 1,
    totalPrice: 510,
  },
  {
    wineName: 'Mazis-Chambertin, Faiveley',
    wineRegion: 'Burgundy (Red)',
    unitSize: '6x75cl',
    wineVintage: 2018,
    qty: 1,
    totalPrice: 790,
  },
  {
    wineName: 'Gevrey-Chambertin Les Champeaux, O. Bernstein',
    wineRegion: 'Burgundy (Red)',
    unitSize: '3x75cl',
    wineVintage: 2019,
    qty: 1,
    totalPrice: 675,
  },
  {
    wineName: 'Latricières-Chambertin, J. M. Fourrier',
    wineRegion: 'Burgundy (Red)',
    unitSize: '6x75cl',
    wineVintage: 2017,
    qty: 1,
    totalPrice: 1050,
  },
  {
    wineName: 'Corton Rognet, Taupenot-Merme',
    wineRegion: 'Burgundy (Red)',
    unitSize: '6x75cl',
    wineVintage: 2019,
    qty: 1,
    totalPrice: 600,
  },
  {
    wineName: 'Corton-Charlemagne, Ponsot',
    wineRegion: 'Burgundy (White)',
    unitSize: '6x75cl',
    wineVintage: 2012,
    qty: 1,
    totalPrice: 980,
  },
  {
    wineName: 'Bollinger Grand Année',
    wineRegion: 'Champagne ',
    unitSize: '6x75cl',
    wineVintage: 2008,
    qty: 1,
    totalPrice: 675,
  },
  {
    wineName: "L'Astre, David Léclapart",
    wineRegion: 'Champagne ',
    unitSize: '6x75cl',
    wineVintage: 2013,
    qty: 1,
    totalPrice: 540,
  },
  {
    wineName: 'Brunello di Montalcino Madonna delle Grazie, Marroneto',
    wineRegion: 'Italy ',
    unitSize: '6x75cl',
    wineVintage: 2012,
    qty: 1,
    totalPrice: 945,
  },

];

So, for example, the output array will hold the data in a similar format as above but the multiple objects that have wineRegion: 'Bordeaux (Red)' will only appear once in the output array and the totalPrice will be the sum of all the totalPrice values. So loop through the array and if a duplicate value exists for regionName, increment the totalPrice.

I have tried to use reduce but couldn't solve this myself.

ikhvjs · Accepted Answer · 2021-07-29 11:36:16Z

You can use reduce() with a Map object.

data.reduce() will return a Map Object and you can use .values() to get the values of the Map object.

Then you can use the spread operator ... to get the values of Map object in an array.

In short:

const output = [...data.reduce().values()]

const data = [ { wineName: "Château Pape-Clément", wineRegion: "Bordeaux (Red)", unitSize: "12x75cl", wineVintage: 2010, qty: 1, totalPrice: 1650, }, { wineName: "Château Beauséjour Duffau-Lagarrosse", wineRegion: "Bordeaux (Red)", unitSize: "6x75cl", wineVintage: 2010, qty: 1, totalPrice: 1400, }, { wineName: "Vosne-Romanée, Berthaut", wineRegion: "Burgundy (Red)", unitSize: "12x75cl", wineVintage: 2017, qty: 1, totalPrice: 510, }, { wineName: "Mazis-Chambertin, Faiveley", wineRegion: "Burgundy (Red)", unitSize: "6x75cl", wineVintage: 2018, qty: 1, totalPrice: 790, }, { wineName: "Gevrey-Chambertin Les Champeaux, O. Bernstein", wineRegion: "Burgundy (Red)", unitSize: "3x75cl", wineVintage: 2019, qty: 1, totalPrice: 675, }, { wineName: "Latricières-Chambertin, J. M. Fourrier", wineRegion: "Burgundy (Red)", unitSize: "6x75cl", wineVintage: 2017, qty: 1, totalPrice: 1050, }, { wineName: "Corton Rognet, Taupenot-Merme", wineRegion: "Burgundy (Red)", unitSize: "6x75cl", wineVintage: 2019, qty: 1, totalPrice: 600, }, { wineName: "Corton-Charlemagne, Ponsot", wineRegion: "Burgundy (White)", unitSize: "6x75cl", wineVintage: 2012, qty: 1, totalPrice: 980, }, { wineName: "Bollinger Grand Année", wineRegion: "Champagne ", unitSize: "6x75cl", wineVintage: 2008, qty: 1, totalPrice: 675, }, { wineName: "L'Astre, David Léclapart", wineRegion: "Champagne ", unitSize: "6x75cl", wineVintage: 2013, qty: 1, totalPrice: 540, }, { wineName: "Brunello di Montalcino Madonna delle Grazie, Marroneto", wineRegion: "Italy ", unitSize: "6x75cl", wineVintage: 2012, qty: 1, totalPrice: 945, }, ];

const o = [
  ...data
    .reduce((a, b) => {
      if (a.has(b.wineRegion)) {
        const obj = a.get(b.wineRegion);
        obj.totalPrice += b.totalPrice;
        a.set(b.wineRegion, obj);
      } else {
        a.set(b.wineRegion, {
          wineRegion: b.wineRegion,
          totalPrice: b.totalPrice,
        });
      }
      return a;
    }, new Map())
    .values(),
];

console.log(o);

Harsh Saini · Accepted Answer · 2021-07-29 11:39:50Z

let newArr = new Map();
data.forEach(x=>{
    if(newArr.has(x.wineRegion)){
        let existingData = newArr.get(x.wineRegion);
        existingData.totalPrice+=x.totalPrice;
    }else{
        newArr.set(x.wineRegion, x);
    }
})

let result = Array.from(newArr.values());

const data = [ { wineName: 'Château Pape-Clément', wineRegion: 'Bordeaux (Red)', unitSize: '12x75cl', wineVintage: 2010, qty: 1, totalPrice: 1650, }, { wineName: 'Château Beauséjour Duffau-Lagarrosse', wineRegion: 'Bordeaux (Red)', unitSize: '6x75cl', wineVintage: 2010, qty: 1, totalPrice: 1400, }, { wineName: 'Vosne-Romanée, Berthaut', wineRegion: 'Burgundy (Red)', unitSize: '12x75cl', wineVintage: 2017, qty: 1, totalPrice: 510, }, { wineName: 'Mazis-Chambertin, Faiveley', wineRegion: 'Burgundy (Red)', unitSize: '6x75cl', wineVintage: 2018, qty: 1, totalPrice: 790, }, { wineName: 'Gevrey-Chambertin Les Champeaux, O. Bernstein', wineRegion: 'Burgundy (Red)', unitSize: '3x75cl', wineVintage: 2019, qty: 1, totalPrice: 675, }, { wineName: 'Latricières-Chambertin, J. M. Fourrier', wineRegion: 'Burgundy (Red)', unitSize: '6x75cl', wineVintage: 2017, qty: 1, totalPrice: 1050, }, { wineName: 'Corton Rognet, Taupenot-Merme', wineRegion: 'Burgundy (Red)', unitSize: '6x75cl', wineVintage: 2019, qty: 1, totalPrice: 600, }, { wineName: 'Corton-Charlemagne, Ponsot', wineRegion: 'Burgundy (White)', unitSize: '6x75cl', wineVintage: 2012, qty: 1, totalPrice: 980, }, { wineName: 'Bollinger Grand Année', wineRegion: 'Champagne ', unitSize: '6x75cl', wineVintage: 2008, qty: 1, totalPrice: 675, }, { wineName: "L'Astre, David Léclapart", wineRegion: 'Champagne ', unitSize: '6x75cl', wineVintage: 2013, qty: 1, totalPrice: 540, }, { wineName: 'Brunello di Montalcino Madonna delle Grazie, Marroneto', wineRegion: 'Italy ', unitSize: '6x75cl', wineVintage: 2012, qty: 1, totalPrice: 945, }, ];

let newArr = new Map();
data.forEach(x=>{
    if(newArr.has(x.wineRegion)){
        let existingData = newArr.get(x.wineRegion);
        existingData.totalPrice+=x.totalPrice;
    }else{
        newArr.set(x.wineRegion, x);
    }
})

let result = Array.from(newArr.values());

console.log(result);

Hi, you can also use SO code snippets for your answer and people can run your codes handier. meta.stackoverflow.com/questions/356678/…

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