Course Schedule IV LeetCode solution in JavaScript

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var checkIfPrerequisite = function (numCourses, prerequisites, queries) {
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  let adj = {};
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  for (let [from, to] of prerequisites) {
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    if (!adj[from]) {
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      adj[from] = [];
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    }
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    adj[from].push(to);
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  }
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  let set = {};
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  Object.keys(adj).forEach((key) => dfs(key));
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  return queries.map(([a, b]) => set[a]?.has(b) || false);
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  function dfs(cur) {
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    if (set[cur]) {
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      return set[cur];
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    }
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    if (!set[cur]) {
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      set[cur] = new Set();
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    }
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    for (let n of adj[cur] || []) {
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      set[cur].add(n);
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      dfs(n);
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      set[n].forEach(set[cur].add, set[cur]);
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    }
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  }
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};