Codility - min avg two slice.js

/**
  given a non-empty array A consisting of N integers, returns the starting position of the slice with the minimal average. If there is more than one slice with a minimal average, you should return the smallest starting position of such a slice.

For example, given array A such that:

    A[0] = 4
    A[1] = 2
    A[2] = 2
    A[3] = 5
    A[4] = 1
    A[5] = 5
    A[6] = 8
the function should return 1, as explained above.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [2..100,000];
each element of array A is an integer within the range [−10,000..10,000].
*/

function solution(A) {
  console.log({A})
    let ndx = 0;
    let min = Number.MAX_VALUE;
    // find min. index for slice of two
    for (var i=0; i<A.length -1; i++) {
        const avg = (A[i] + A[i+1]) / 2;
        if (avg < min) {
            min = avg;
            ndx = i;
            console.log({avg, min, i})
        }
    }


    // find min. index for slice of three
    for (var i=0; i<A.length -2; i++) {
        const avg = (A[i] + A[i+1] + A[i+2]) / 3;
        if (avg < min) {
            min = avg;
            ndx = i;
            console.log({avg, min, i})
        }
    }
    console.log({ndx})

    return ndx;
}