BeautifulArrays

function solve(arr) {
    let sorted = [...arr].sort((a, b) => a - b);
    let swapsAsc = findSwaps([...arr], sorted);
    let swapsDesc = findSwaps([...arr], sorted.reverse());
    return Math.min(swapsAsc, swapsDesc);
}

function findSwaps(arr, sorted) {
    // map value to index
    let value2index = {};
    arr.forEach((val, i) => value2index[val] = i);
    let swaps = 0;
    for (let i = 0; i < arr.length; i++) {
        // At index i there must be value sorted[i]
        if (arr[i] != sorted[i]) {
            // Find the position of value sorted[i] in the input array
            let position = value2index[sorted[i]];
            // Swap sorted[i] with arr[i]
            [arr[i], arr[position]] = [arr[position], arr[i]];
            // Update the position of arr[position] in the value2index map
            value2index[arr[position]] = position;
            // Increment swap count
            swaps++;
        }
    }
    return swaps;
}

console.log(solve([2, 5, 3, 1])); // should return 2