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MongoDB object modeling designed to work in an asynchronous environment.

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Mongoose

Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Mongoose supports both promises and callbacks.

Slack Status Build Status NPM version

npm

Documentation

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.

Support

Plugins

Check out the plugins search site to see hundreds of related modules from the community. Next, learn how to write your own plugin from the docs or this blog post.

Contributors

Pull requests are always welcome! Please base pull requests against the

master
branch and follow the contributing guide.

If your pull requests makes documentation changes, please do not modify any

.html
files. The
.html
files are compiled code, so please make your changes in
docs/*.pug
,
lib/*.js
, or
test/docs/*.js
.

View all 400+ contributors.

Installation

First install Node.js and MongoDB. Then:

$ npm install mongoose

Importing

// Using Node.js `require()`
const mongoose = require('mongoose');

// Using ES6 imports import mongoose from 'mongoose';

Mongoose for Enterprise

Available as part of the Tidelift Subscription

The maintainers of mongoose and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. Learn more.

Overview

Connecting to MongoDB

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.

Defining a Model

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.

Accessing a Model

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

Embedded Documents

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!

Middleware

See the docs page.

Intercepting and mutating method arguments

You can intercept method arguments via middleware.

For example, this would allow you to broadcast changes about your Documents every time someone

set
s 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(); });

Schema gotcha

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 } });

Driver Access

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.

API Docs

Find the API docs here, generated using dox and acquit.

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License

Copyright (c) 2010 LearnBoost <[email protected]>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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