无重复合并数组| nodejs | mongoDb

// 基于Set的去重
function mergeUniqueArrays(arrays) {
  return Array.from(new Set(arrays.flat()));
}

const array1 = [1, 2, 3];
const array2 = [2, 3, 4];
const array3 = [3, 4, 5];

console.log(mergeUniqueArrays([array1, array2, array3])); // 输出: [1, 2, 3, 4, 5]

{ "_id": 1, "tags": ["javascript", "nodejs"] }
{ "_id": 2, "tags": ["nodejs", "mongodb"] }
{ "_id": 3, "tags": ["javascript", "mongodb"] }

db.users.aggregate([
  {
    $project: { tags: 1 }
  },
  {
    $unwind: "$tags"
  },
  {
    $group: {
      _id: "$tags",
      count: { $sum: 1 }
    }
  },
  {
    $sort: { count: -1 }
  },
  {
    $project: {
      _id: 0,
      tag: "$_id",
      count: 1
    }
  }
]);