Javascript Program for Mean of range in array

// Javascript program to find floor value
// of mean in range l to r

// To find mean of range in l to r
function findMean(arr, l, r) {
    // Both sum and count are
    // initialize to 0
    let sum = 0, count = 0;

    // To calculate sum and number
    // of elements in range l to r
    for (let i = l; i <= r; i++) {
        sum += arr[i];
        count++;
    }

    // Calculate floor value of mean
    let mean = Math.floor(sum / count);

    // Returns mean of array
    // in range l to r
    return mean;
}

let arr = [1, 2, 3, 4, 5];
console.log(findMean(arr, 0, 2));
console.log(findMean(arr, 1, 3));
console.log(findMean(arr, 0, 4));

// Javascript program to find floor value
// of mean in range l to r
let MAX = 1000005;
let prefixSum = new Array(MAX);
prefixSum.fill(0);

// To calculate prefixSum of array
function calculatePrefixSum(arr, n) {

    // Calculate prefix sum of array
    prefixSum[0] = arr[0];
    for (let i = 1; i < n; i++)
        prefixSum[i] = prefixSum[i - 1] + arr[i];
}

// To return floor of mean
// in range l to r
function findMean(l, r) {
    if (l == 0)
        return parseInt(Math.floor(prefixSum[r] /
            (r + 1)), 10);

    // Sum of elements in range l to
    // r is prefixSum[r] - prefixSum[l-1]
    // Number of elements in range
    // l to r is r - l + 1
    return parseInt(Math.floor((prefixSum[r] -
        prefixSum[l - 1]) /
        (r - l + 1)), 10);
}

// Driver code
let arr = [1, 2, 3, 4, 5];
let n = arr.length;
calculatePrefixSum(arr, n);

console.log(findMean(1, 2));
console.log(findMean(1, 3));
console.log(findMean(1, 4));