Largest Component Size by Common Factor LeetCode solution in JavaScript

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var largestComponentSize = function (nums) {
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  const rootByFactor = new Map();
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  const parents = new Array(nums.length);
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  function addFactor(i, factor) {
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    if (rootByFactor.has(factor)) {
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      let r = rootByFactor.get(factor);
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      while (parents[i] != i) i = parents[i];
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      while (parents[r] != r) r = parents[r];
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      parents[i] = r;
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    }
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    rootByFactor.set(factor, parents[i]);
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  }
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  for (const [i, num] of nums.entries()) {
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    parents[i] = i;
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    addFactor(i, num);
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    for (let factor = 2; factor * factor <= num; ++factor) {
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      if (num % factor == 0) {
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        addFactor(i, factor);
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        addFactor(i, num / factor);
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      }
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    }
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  }
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  let largest = 0;
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  const sums = new Array(nums.length).fill(0);
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  for (let r of parents) {
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    while (parents[r] != r) r = parents[r];
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    largest = Math.max(largest, ++sums[r]);
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  }
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  return largest;
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};