Determine the number of occurrences of specific values within a group of objects based on a

Question

Determine the number of occurrences of specific values within a group of objects based on a

I have the following dataset:

const data2 = [
{
  App: "testa.com",
  Name: "TEST A",
  Category: "HR", 
  Employees: 7
},
{
  App: "testd.com",
  Name: "TEST D",
  Category: "DevOps", 
  Employees: 7
},
{
  App: "teste.com",
  Name: "TEST E",
  Category: "DevOps", 
  Employees: 7
},
{
  App: "testf.com",
  Name: "TEST F",
  Category: "Business", 
  Employees: 7
}
]

I am trying to extract the count of unique categories from this data. Currently, I can list all distinct categories but I am struggling to calculate their respective counts.

The code snippet below helps me in getting the Unique Categories:

  let uniqueCategory = [];
  for(let i = 0; i < result.data.length; i++){    
      if(uniqueCategory.indexOf(result.data[i].Category) === -1){
        uniqueCategory.push(result.data[i].Category);        
      }        
  }

What modifications do I need to make in order to obtain the Counts of each Category in the uniqueCategory array? The desired output should resemble something like this:

uniqueCategory = [
  {Category: "DevOps", count: 5},
  {Category: "Business", count: 4},
  ....
  {}
]

javascript arrays

Answer 1

Answer №1

Your current method involves iterating over your source array (using `.indexOf()`) in each iteration of the `for(..` loop. This can slow down the lookup process unnecessarily.

Instead, consider utilizing the Array.prototype.reduce() function to iterate over your source array and construct a Map. This Map will have `Category` as the key and an object in the desired format as the value. You can then extract the values using Map.prototype.values() into the resulting array.

This approach will enhance performance significantly and offer better scalability.

const src = [{App:"testa.com",Name:"TEST A",Category:"HR",Employees:7},{App:"testd.com",Name:"TEST D",Category:"DevOps",Employees:7},{App:"teste.com",Name:"TEST E",Category:"DevOps",Employees:7},{App:"testf.com",Name:"TEST F",Category:"Business",Employees:7}],

      result = [...src
        .reduce((r, {Category}) => {
          const cat = r.get(Category)
          cat ? cat.count ++ : r.set(Category, {Category, count: 1})
          return r
        }, new Map)
        .values()
      ]
    
console.log(result)

.as-console-wrapper{min-height:100%;}

Answer 2

Your current method involves iterating over your source array (using `.indexOf()`) in each iteration of the `for(..` loop. This can slow down the lookup process unnecessarily.

Instead, consider utilizing the Array.prototype.reduce() function to iterate over your source array and construct a Map. This Map will have `Category` as the key and an object in the desired format as the value. You can then extract the values using Map.prototype.values() into the resulting array.

This approach will enhance performance significantly and offer better scalability.

const src = [{App:"testa.com",Name:"TEST A",Category:"HR",Employees:7},{App:"testd.com",Name:"TEST D",Category:"DevOps",Employees:7},{App:"teste.com",Name:"TEST E",Category:"DevOps",Employees:7},{App:"testf.com",Name:"TEST F",Category:"Business",Employees:7}],

      result = [...src
        .reduce((r, {Category}) => {
          const cat = r.get(Category)
          cat ? cat.count ++ : r.set(Category, {Category, count: 1})
          return r
        }, new Map)
        .values()
      ]
    
console.log(result)

.as-console-wrapper{min-height:100%;}

Answer 3

Answer №2

The most efficient method is utilizing the Array.prototype.reduce function

const arr = [ ... ];
const result = arr.reduce((accumulator, item) => {
  if (!accumulator[item.type]) {
    accumulator[item.type] = 0;
  }

  accumulator[item.type]++;

  return accumulator;
}, {});
console.log(result); // this will display the desired output

Answer 4

The most efficient method is utilizing the Array.prototype.reduce function

const arr = [ ... ];
const result = arr.reduce((accumulator, item) => {
  if (!accumulator[item.type]) {
    accumulator[item.type] = 0;
  }

  accumulator[item.type]++;

  return accumulator;
}, {});
console.log(result); // this will display the desired output

Answer 5

Answer №3

Here is an alternative approach utilizing .map along with Set:

const data = [
{
  Site: "example1.com",
  Name: "Example 1",
  Category: "Tech", 
  Employees: 10
},
{
  Site: "example2.com",
  Name: "Test 2",
  Category: "Marketing", 
  Employees: 20
},
{
  Site: "example3.com",
  Name: "Example 3",
  Category: "Tech", 
  Employees: 15
},
{
  Site: "example4.com",
  Name: "Test 4",
  Category: "HR", 
  Employees: 30
}
];

const categoriesList = data.map(item => item.Category);
const uniqueCategories = [...new Set(categoriesList)];
console.log(uniqueCategories.length);

Answer 6

Here is an alternative approach utilizing .map along with Set:

const data = [
{
  Site: "example1.com",
  Name: "Example 1",
  Category: "Tech", 
  Employees: 10
},
{
  Site: "example2.com",
  Name: "Test 2",
  Category: "Marketing", 
  Employees: 20
},
{
  Site: "example3.com",
  Name: "Example 3",
  Category: "Tech", 
  Employees: 15
},
{
  Site: "example4.com",
  Name: "Test 4",
  Category: "HR", 
  Employees: 30
}
];

const categoriesList = data.map(item => item.Category);
const uniqueCategories = [...new Set(categoriesList)];
console.log(uniqueCategories.length);

Determine the number of occurrences of specific values within a group of objects based on a

Answer №1

Answer №2

Answer №3

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