Sum all duplicate value in array

We are required to write a JavaScript function that takes in an array of numbers with duplicate entries and sums all the duplicate entries to one index

For example −

If the input array is −

const input = [1, 3, 1, 3, 5, 7, 5, 4];

Then the output should be −

const output = [2, 6, 7, 10, 4];

Example

Let’s write the code −

const input = [1, 3, 1, 3, 5, 7, 5, 3, 4];
const sumDuplicate = arr => {
   const map = arr.reduce((acc, val) => {
      if(acc.has(val)){
         acc.set(val, acc.get(val) + 1);
      }else{
         return acc;
      }, new Map());
   }
   return Array.from(map, el => el[0] * el[1]);
};
console.log(sumDuplicate(input));

Output

Following is the output in the console −

[ 2, 9, 10, 7, 4 ]

Sum all duplicate value in array - JavaScript

Example

Output