MongoDB :使用Mongoose统计每年的文档

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/mydatabase', { useNewUrlParser: true });

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const documentSchema = new Schema({
  title: String,
  year: Number,
  // 其他字段...
});

const Document = mongoose.model('Document', documentSchema);

const mongoose = require('mongoose');
const Document = require('./models/document');

Document.aggregate([
  {
    $group: {
      _id: '$year',
      count: { $sum: 1 }
    }
  },
  {
    $sort: { _id: 1 }
  }
])
.then(results => {
  console.log(results);
})
.catch(error => {
  console.error(error);
});