find the standard deviation of all keys in a map in typescript

index.ts
let map = new Map<number, number>(); // initialize your map

let sum = 0;
let sumSquared = 0;
let count = 0;

map.forEach((value, key) => {
  sum += key;
  sumSquared += key * key;
  count += 1;
});

const mean = sum / count;
const variance = (sumSquared / count) - (mean * mean);
const stdDev = Math.sqrt(variance);

console.log(stdDev);
339 chars
18 lines

index.ts
mean = sum / count
variance = (sumSquared / count) - (mean * mean)
stdDev = Math.sqrt(variance)
96 chars
4 lines