Determine the occurrences of each element in a given array and save them as key-value pairs

Question

Determine the occurrences of each element in a given array and save them as key-value pairs

Is there a way to efficiently convert an array of elements into an object with key value pairs representing element frequencies? For example, given an array:

     var array = ['a','a','a','b','b','c','d','d','d','d',]

I want to transform it into an object like this:

     obj = [{ element: 'a', frequency: 3}, 
            { element: 'b', frequency: 2},
            { element: 'c', frequency: 1},
            { element: 'd', frequency: 4}]

Instead of the above format, I currently have a solution that provides the following output:

       obj = { a : 3, b : 2, c : 1, d : 4 }

javascript arrays object

Answer 1

Answer №1

If you want to transform it, you can utilize the Object.entries method as demonstrated below.

const myObj = {
  x: 5,
  y: 7,
  z: 2,
  w: 9
};

const result = Object.entries(myObj).map(item => ({
  key: item[0],
  value: item[1]
}));
console.log(result);

Answer 2

If you want to transform it, you can utilize the Object.entries method as demonstrated below.

const myObj = {
  x: 5,
  y: 7,
  z: 2,
  w: 9
};

const result = Object.entries(myObj).map(item => ({
  key: item[0],
  value: item[1]
}));
console.log(result);

Answer 3

Answer №2

If you want to manipulate an object using JavaScript, consider using Array#map in conjunction with Object.entries and destructuring.

const obj = { x : 5, y : 6, z : 7, w : 8 };
const result = Object.entries(obj).map(([key, value])=>({key, value}));
console.log(result);

Answer 4

If you want to manipulate an object using JavaScript, consider using Array#map in conjunction with Object.entries and destructuring.

const obj = { x : 5, y : 6, z : 7, w : 8 };
const result = Object.entries(obj).map(([key, value])=>({key, value}));
console.log(result);

Answer 5

Answer №3

Utilizing a map for easy and quick access while calculating the frequencies is a clever approach, but have you ever considered generating the desired objects directly?

For example, instead of:

{ a: 3
, b: 2
}

Why not try this instead?

{ a: {element: 'a', frequency: 3}
, b: {element: 'b', frequency: 2}
}

By doing so, you can simply use Object.values(obj) to achieve your desired outcome.

const freq =
  xs =>
    Object.values
      ( xs.reduce
          ( (acc, x) =>
              ( acc[x] = acc[x] || {element: x, frequency: 0}
              , acc[x].frequency += 1
              , acc
              )
          , {}
          )
      );
      
      
console.log(freq(['a','a','a','b','b','c','d','d','d','d']));

Answer 6

Utilizing a map for easy and quick access while calculating the frequencies is a clever approach, but have you ever considered generating the desired objects directly?

For example, instead of:

{ a: 3
, b: 2
}

Why not try this instead?

{ a: {element: 'a', frequency: 3}
, b: {element: 'b', frequency: 2}
}

By doing so, you can simply use Object.values(obj) to achieve your desired outcome.

const freq =
  xs =>
    Object.values
      ( xs.reduce
          ( (acc, x) =>
              ( acc[x] = acc[x] || {element: x, frequency: 0}
              , acc[x].frequency += 1
              , acc
              )
          , {}
          )
      );
      
      
console.log(freq(['a','a','a','b','b','c','d','d','d','d']));

Determine the occurrences of each element in a given array and save them as key-value pairs

Answer №1

Answer №2

Answer №3

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