Count all values in object where X is the first key letter

April 27, 2022

I would like to count all values where a letter appears first and return the letter with atleast half of all values in my object so for example I assuming I have an object like this

const sample = { "A,B,C": 4, "B,C,A": 3, "C,B,A": 2, "A,C,B": 2 };

I would return A because if you count all the values where A appears first you would get 6 (4+2)

This is what I currently have:

for (let votes of Object.values(sample)) {
  sum += votes
}
stretchWin = Math.round(sum / 2)
winner = Object.entries(sample)
  .filter(([, val]) => val >= stretchWin)
  .map(([keys]) => keys)

With this I am getting an empty array because I am not counting all the values assigned to A

>Solution :

Iterate over the whole sample first to get a sum of the values by the first letter first, then iterate over that new object to identify which values match the target of half the total.

const sample = {
  "A,B,C": 4,
  "B,C,A": 3,
  "C,B,A": 2,
  "A,C,B": 2
};
const sumByChar = {};
for (const [key, value] of Object.entries(sample)) {
  const char = key[0];
  sumByChar[char] = (sumByChar[char] ?? 0) + value;
}
let sum = 0;
for (let votes of Object.values(sample)) {
  sum += votes
}
const targetSum = Math.round(sum / 2);
const winners = Object.entries(sumByChar)
  .filter(([, val]) => val >= targetSum)
  .map(([key]) => key);
console.log(winners);