Degree of an Array LeetCode solution in JavaScript

1
/**
2
 * 1. compute all positions for each number
3
 * 2. filter arrays of max length
4
 * 3. select minimum difference between its first and last elems
5
 */
6
var findShortestSubArray = function (nums) {
7
  const numPositions = {};
8
  for (let i = 0; i < nums.length; i++) {
9
    const num = nums[i];
10
    if (numPositions[num] == null) numPositions[num] = [];
11
    numPositions[num].push(i);
12
  }
13

14
  let maxLen = 0;
15
  // will store the positions of most frequent numbers
16
  let maxPos = [];
17
  for (const positions of Object.values(numPositions)) {
18
    const curLen = positions.length;
19
    if (curLen === maxLen) {
20
      maxPos.push(positions);
21
    } else if (curLen > maxLen) {
22
      maxLen = curLen;
23
      maxPos = [positions];
24
    }
25
  }
26

27
  let minDist = Number.MAX_SAFE_INTEGER;
28
  for (const positions of maxPos) {
29
    minDist = Math.min(
30
      minDist,
31
      positions[positions.length - 1] - positions[0] + 1
32
    );
33
  }
34
  return minDist;
35
};