Shortest ways to find Mode (highest occurring element & it's frequency)

array_mode_fastest.js

// This is most concise I could get without compromising on speed.

const arr = [1, 5, 2, 2, 5, 5, 6, 6, 5, 6, 6, 2, 3, 3, 5, 3];

let f = new Map();
for (let i = 0; i < arr.length; i++)
    f.set(arr[i], f.has(arr[i]) ? f.get(arr[i]) + 1 : 1);

let l = arr[0];
for (let i = 1; i < arr.length; i++)
    if(f.get(l) < f.get(arr[i-1])) l = arr[i];

array_mode_one-loop.js

// This version mutates the input. 
// I don't know why, but it just felt good not using another array.

const arr = [1, 5, 2, 2, 5, 5, 6, 6, 5, 6, 6, 2, 3, 3, 5, 3];
const size = arr.length;

for (let i = 0; i < size; i++) {
  arr[i + size] = arr[arr.indexOf(arr[i]) + size]++ || 1;
}

const frequencies = arr.splice(size, size*2)
const maxFrequency = Math.max(...frequencies);
const element = arr[frequencies.indexOf(maxFrequency)];