Count Unreachable Pairs of Nodes in an Undirected Graph LeetCode solution in JavaScript

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var countPairs = function (n, edges) {
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  const adj = [];
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  for (let i = 0; i < n; i++) {
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    adj.push([]);
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  }
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  for (let [from, to] of edges) {
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    adj[from].push(to);
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    adj[to].push(from);
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  }
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  const visited = new Set();
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  function dfs(from) {
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    visited.add(from);
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    let count = 1;
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    for (const to of adj[from]) {
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      if (!visited.has(to)) {
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        count += dfs(to);
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      }
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    }
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    return count;
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  }
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  const groups = [];
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  for (let i = 0; i < n; i++) {
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    if (!visited.has(i)) {
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      const count = dfs(i);
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      groups.push(count);
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    }
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  }
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  let ans = 0;
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  for (let i = 0; i < groups.length - 1; i++) {
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    for (let j = i + 1; j < groups.length; j++) {
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      ans += groups[i] * groups[j];
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    }
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  }
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  return ans;
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};