Mongoose is an Object Data Modeling (ODM) library for MongoDB and Node.js. It manages relationships between data, provides schema validation, and is used to translate between objects in code and the representation of those objects in MongoDB.
Schema Definition
Defines a schema for a collection with various field types, validation, and defaults.
{"const mongoose = require('mongoose');\nconst Schema = mongoose.Schema;\nconst blogSchema = new Schema({\n title: String,\n author: String,\n body: String,\n comments: [{ body: String, date: Date }],\n date: { type: Date, default: Date.now },\n hidden: Boolean,\n meta: {\n votes: Number,\n favs: Number\n }\n});"}Model Creation
Creates a model based on a defined schema, which can then be used to create, read, update, and delete documents of that schema type.
{"const mongoose = require('mongoose');\nconst Blog = mongoose.model('Blog', blogSchema);"}Connection to MongoDB
Establishes a connection to a MongoDB database.
{"const mongoose = require('mongoose');\nmongoose.connect('mongodb://localhost/my_database', {useNewUrlParser: true, useUnifiedTopology: true});"}Querying
Queries the database for documents matching certain criteria.
{"Blog.find({ author: 'John Doe' }).exec((err, blogs) => {\n if (err) return handleError(err);\n console.log('The blogs are', blogs);\n});"}Data Validation
Ensures that the data being saved to the database meets certain criteria defined in the schema.
{"const personSchema = new Schema({\n name: {\n type: String,\n required: true\n },\n age: {\n type: Number,\n min: 18,\n max: 65\n }\n});"}Middleware (Hooks)
Allows execution of code before or after certain actions, such as saving a document.
{"blogSchema.pre('save', function(next) {\n if (!this.isModified('title')) {\n return next();\n }\n this.modifiedAt = Date.now();\n next();\n});"}Sequelize is a promise-based Node.js ORM for Postgres, MySQL, MariaDB, SQLite, and Microsoft SQL Server. It features solid transaction support, relations, eager and lazy loading, read replication and more. Unlike Mongoose, which is designed for MongoDB, Sequelize is used for relational databases.
TypeORM is an ORM that can run in Node.js and be used with TypeScript and JavaScript (ES5, ES6, ES7, ES8). It supports both Active Record and Data Mapper patterns, unlike Mongoose which is primarily schema-based. TypeORM works with SQL databases like MySQL, PostgreSQL, and SQLite.
Waterline is a data store-agnostic ORM that is bundled in the Sails.js framework but can also be used separately. It provides a uniform API for accessing different kinds of databases, including both SQL and NoSQL, and thus offers more flexibility compared to Mongoose which is MongoDB-specific.
Bookshelf is a JavaScript ORM for Node.js, built on the Knex SQL query builder. It features both promise-based and traditional callback interfaces, transaction support, and eager/nested-eager relation loading. Bookshelf is designed for relational databases and thus is a different choice compared to Mongoose for MongoDB.
Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Mongoose supports both promises and callbacks.
The official documentation website is mongoosejs.com.
Mongoose 5.0.0 was released on January 17, 2018. You can find more details on backwards breaking changes in 5.0.0 on our docs site.
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First install Node.js and MongoDB. Then:
$ npm install mongoose
// Using Node.js `require()`
const mongoose = require('mongoose');
// Using ES6 imports
import mongoose from 'mongoose';
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First, we need to define a connection. If your app uses only one database, you should use mongoose.connect. If you need to create additional connections, use mongoose.createConnection.
Both connect and createConnection take a mongodb:// URI, or the parameters host, database, port, options.
await mongoose.connect('mongodb://localhost/my_database', {
useNewUrlParser: true,
useUnifiedTopology: true,
useFindAndModify: false,
useCreateIndex: true
});
Once connected, the open event is fired on the Connection instance. If you're using mongoose.connect, the Connection is mongoose.connection. Otherwise, mongoose.createConnection return value is a Connection.
Note: If the local connection fails then try using 127.0.0.1 instead of localhost. Sometimes issues may arise when the local hostname has been changed.
Important! Mongoose buffers all the commands until it's connected to the database. This means that you don't have to wait until it connects to MongoDB in order to define models, run queries, etc.
Models are defined through the Schema interface.
const Schema = mongoose.Schema;
const ObjectId = Schema.ObjectId;
const BlogPost = new Schema({
author: ObjectId,
title: String,
body: String,
date: Date
});
Aside from defining the structure of your documents and the types of data you're storing, a Schema handles the definition of:
The following example shows some of these features:
const Comment = new Schema({
name: { type: String, default: 'hahaha' },
age: { type: Number, min: 18, index: true },
bio: { type: String, match: /[a-z]/ },
date: { type: Date, default: Date.now },
buff: Buffer
});
// a setter
Comment.path('name').set(function (v) {
return capitalize(v);
});
// middleware
Comment.pre('save', function (next) {
notify(this.get('email'));
next();
});
Take a look at the example in examples/schema/schema.js for an end-to-end example of a typical setup.
Once we define a model through mongoose.model('ModelName', mySchema), we can access it through the same function
const MyModel = mongoose.model('ModelName');
Or just do it all at once
const MyModel = mongoose.model('ModelName', mySchema);
The first argument is the singular name of the collection your model is for. Mongoose automatically looks for the plural version of your model name. For example, if you use
const MyModel = mongoose.model('Ticket', mySchema);
Then Mongoose will create the model for your tickets collection, not your ticket collection.
Once we have our model, we can then instantiate it, and save it:
const instance = new MyModel();
instance.my.key = 'hello';
instance.save(function (err) {
//
});
Or we can find documents from the same collection
MyModel.find({}, function (err, docs) {
// docs.forEach
});
You can also findOne, findById, update, etc.
const instance = await MyModel.findOne({ ... });
console.log(instance.my.key); // 'hello'
For more details check out the docs.
Important! If you opened a separate connection using mongoose.createConnection() but attempt to access the model through mongoose.model('ModelName') it will not work as expected since it is not hooked up to an active db connection. In this case access your model through the connection you created:
const conn = mongoose.createConnection('your connection string');
const MyModel = conn.model('ModelName', schema);
const m = new MyModel;
m.save(); // works
vs
const conn = mongoose.createConnection('your connection string');
const MyModel = mongoose.model('ModelName', schema);
const m = new MyModel;
m.save(); // does not work b/c the default connection object was never connected
In the first example snippet, we defined a key in the Schema that looks like:
comments: [Comment]
Where Comment is a Schema we created. This means that creating embedded documents is as simple as:
// retrieve my model
const BlogPost = mongoose.model('BlogPost');
// create a blog post
const post = new BlogPost();
// create a comment
post.comments.push({ title: 'My comment' });
post.save(function (err) {
if (!err) console.log('Success!');
});
The same goes for removing them:
BlogPost.findById(myId, function (err, post) {
if (!err) {
post.comments[0].remove();
post.save(function (err) {
// do something
});
}
});
Embedded documents enjoy all the same features as your models. Defaults, validators, middleware. Whenever an error occurs, it's bubbled to the save() error callback, so error handling is a snap!
See the docs page.
You can intercept method arguments via middleware.
For example, this would allow you to broadcast changes about your Documents every time someone sets a path in your Document to a new value:
schema.pre('set', function (next, path, val, typel) {
// `this` is the current Document
this.emit('set', path, val);
// Pass control to the next pre
next();
});
Moreover, you can mutate the incoming method arguments so that subsequent middleware see different values for those arguments. To do so, just pass the new values to next:
.pre(method, function firstPre (next, methodArg1, methodArg2) {
// Mutate methodArg1
next("altered-" + methodArg1.toString(), methodArg2);
});
// pre declaration is chainable
.pre(method, function secondPre (next, methodArg1, methodArg2) {
console.log(methodArg1);
// => 'altered-originalValOfMethodArg1'
console.log(methodArg2);
// => 'originalValOfMethodArg2'
// Passing no arguments to `next` automatically passes along the current argument values
// i.e., the following `next()` is equivalent to `next(methodArg1, methodArg2)`
// and also equivalent to, with the example method arg
// values, `next('altered-originalValOfMethodArg1', 'originalValOfMethodArg2')`
next();
});
type, when used in a schema has special meaning within Mongoose. If your schema requires using type as a nested property you must use object notation:
new Schema({
broken: { type: Boolean },
asset: {
name: String,
type: String // uh oh, it broke. asset will be interpreted as String
}
});
new Schema({
works: { type: Boolean },
asset: {
name: String,
type: { type: String } // works. asset is an object with a type property
}
});
Mongoose is built on top of the official MongoDB Node.js driver. Each mongoose model keeps a reference to a native MongoDB driver collection. The collection object can be accessed using YourModel.collection. However, using the collection object directly bypasses all mongoose features, including hooks, validation, etc. The one
notable exception that YourModel.collection still buffers
commands. As such, YourModel.collection.find() will not
return a cursor.
Find the API docs here, generated using dox and acquit.
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FAQs
Mongoose MongoDB ODM
The npm package mongoose receives a total of 2,244,988 weekly downloads. As such, mongoose popularity was classified as popular.
We found that mongoose demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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