mongoose arrayFilters

arrayFilters.js

import mongoose from 'mongoose';

run().catch(error => console.error(error.stack));

async function run() {
  await mongoose.connect('mongodb://localhost:27017/test');

  await mongoose.connection.dropDatabase();

  const BlogPost = mongoose.model('BlogPost', new mongoose.Schema({
    title: String,
    comments: [{ _id: false, author: String, text: String }]
  }), 'BlogPost');

  // Insert 2 docs
  await BlogPost.create({
    title: 'A Node.js Perspective on MongoDB 3.6: Array Filters',
    comments: [
      { author: 'Foo', text: 'This is awesome!' },
      { author: 'Bar', text: 'Where are the upgrade docs?' }
    ]
  });

  await BlogPost.create({
    title: 'What\'s New in Mongoose 5: Improved Connections',
    comments: [
      { author: 'Bar', text: 'Thanks!' },
      { author: 'Bar', text: 'Sorry for double post' }
    ]
  });

  // Update docs using `arrayFilters` and `$[]`
  await BlogPost.updateMany({ 'comments.author': 'Bar' },
    { $set: { 'comments.$[element].author': 'Baz' } },
    // `$[element]` is tied to name `element` below
    { arrayFilters: [{ 'element.author': 'Bar' }] });

  const docs = await BlogPost.find();
  // [ [ { author: 'Foo', text: 'This is awesome!' },
  //     { author: 'Baz', text: 'Where are the upgrade docs?' } ],
  //   [ { author: 'Baz', text: 'Thanks!' },
  //     { author: 'Baz', text: 'Sorry for double post' } ] ]
  console.log(docs.map(doc => doc.comments));
}