How to group objects by some property while summing another-CodePudding

I try many ways to solve this. I can remove duplicate values. but the problem is updating total_product value. How can I do this? Give me some hints.

This is my Main Array :

 const colors = [
    { "name": "Black", "total_product": 1 },
    { "name": "Black", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 },    
]

I Want Like This :

 const colors = [
    { "name": "Black", "total_product": 2 },
    { "name": "White", "total_product": 4 }         
]

CodePudding user response：

It's a good case for reduce which "boils down" an array to an accumulator value. Here, reduce (doc) can be used to create objects that count occurrences of each name...

const colors = [
    { "name": "Black", "total_product": 1 },
    { "name": "Black", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 },
    { "name": "White", "total_product": 1 } 
];

const counts = colors.reduce((acc, obj) => {
  if (!acc[obj.name]) acc[obj.name] = { name: obj.name, total_product: 0 };
  acc[obj.name].total_product  ;
  return acc;
}, {});
const result = Object.values(counts);
console.log(result);

The intermediate value counts produced by reduce looks like this...

{
  "Black": {
    "name": "Black",
    "total_product": 2 // <- incremented each time we found a "Black"
  },
  "White": {
    "name": "White",
    "total_product": 4 // <- incremented each time we found a "White"
  }
}

Object.values(), like the name implies, makes an array of the values.

CodePudding user response：

You can use new Map() or simple object to store the count of same objects:

const colors = [
  { "name": "Black", "total_product": 1 },
  { "name": "Black", "total_product": 1 },
  { "name": "White", "total_product": 1 },
  { "name": "White", "total_product": 1 },
  { "name": "White", "total_product": 1 },
  { "name": "White", "total_product": 1 },    
];

const colorsMap = new Map();

colors.forEach(color => {
  
  if (colorsMap.has(color.name)) {
    colorsMap.set(color.name, colorsMap.get(color.name)   1);
    return;
  }
  
  colorsMap.set(color.name, 1);
});

const groupedColors = [];

colorsMap.forEach((value, key) => {
  groupedColors.push({
    name: key,
    total_product: value
  });
})

console.log(groupedColors);

CodePudding user response：

It makes no sense to return an Array since you already squashed the array to unique names and their respective values, simply reduce to Object:

const colors = [
  {name:"Black", total_product:1},
  {name:"Black", total_product:1},
  {name:"White", total_product:1},
  {name:"White", total_product:1},
  {name:"White", total_product:1},
  {name:"White", total_product:1},    
];

const sumColors = colors.reduce((ob, item) => {
  ob[item.name] ??= 0
  ob[item.name]  = item.total_product;
  return ob;
}, {});

console.log(sumColors); // {"Black": 2, "White": 4}

CodePudding user response：

const colors = [
  { name: "Black", total_product: 1 },
  { name: "Black", total_product: 1 },
  { name: "White", total_product: 1 },
  { name: "White", total_product: 1 },
  { name: "White", total_product: 1 },
  { name: "White", total_product: 1 }
];

const uniqueColors = (colors) => {
  const unique = [];
  colors.map((color) => {
    const index = unique.findIndex((c) => c.name === color.name);
    if (index === -1) {
      unique.push(color);
    } else {
      unique[index].total_product  ;
    }
  });
  return unique;
};

console.log(uniqueColors(colors));