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MongoDB

Using MongoDB with Mongoose — Data Manipulation with Models

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To make MongoDB database manipulation easy, we can use the Mongoose NPM package to make working with MongoDB databases easier.

In this article, we’ll look at how to use Mongoose to manipulate our MongoDB database.

Models

We can create models so we can use them as templates to create a document in the MongoDB database.

For example, we can write:

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/test')
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = mongoose.model('Tank', schema);
const small = new Tank({ size: 'small' });
small.save((err) => {
  if (err) {
    return console.log(err);
  }
});

We called mongoose.Schema that has the name and size string fields.

Then we create the model with the schema with the mongoose.model method.

Next, we use the model class to create the document with the data we want.

Then we call save to save the document.

The tank collection will be created if it’s not already created.

Then the document will be created.

The callback we pass into the save method has the err parameter that will be defined if there’s an error.

We can also add the create static method to create the document:

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/test')
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = mongoose.model('Tank', schema);
Tank.create({ size: 'small' }, (err, small) => {
  if (err) {
    return console.log(err);
  }
  console.log(small);
});

The first argument is the document we want to create.

And the 2nd argument is the callback that’s called when the result is computed.

Also, we can call the insertMany static method on the Tank model:

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/test')
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = mongoose.model('Tank', schema);
Tank.insertMany([{ size: 'small' }], (err) => {
  if (err) {
    console.log(err);
  }
});

If we create a custom collection, then we can use the model function to create the model:

const mongoose = require('mongoose');
const connection = mongoose.createConnection('mongodb://localhost:27017/test');
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = connection.model('Tank', schema);
Tank.insertMany([{ size: 'small' }], (err) => {
  if (err) {
    console.log(err);
  }
});

Querying

We can query documents with the find method.

For example, we can write:

const mongoose = require('mongoose');
const connection = mongoose.createConnection('mongodb://localhost:27017/test');
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = connection.model('Tank', schema);
Tank.find({ size: 'small' }).where('createdDate').gt(365).exec((err, tanks) => {
  if (err) {
    return console.log(err)
  }
  console.log(tanks);
});

We call find with the key and value we’re looking for.

The where method has the field that we want to search for.

gt searches for something that’s greater than.

exec runs the query, and the callback has the results.

Deleting

We can delete items with the deleteOne method:

const mongoose = require('mongoose');
const connection = mongoose.createConnection('mongodb://localhost:27017/test');
const schema = new mongoose.Schema({ name: 'string', size: 'string' });
const Tank = connection.model('Tank', schema);
Tank.deleteOne({ size: 'large' }, (err) => {
  if (err) {
    return console.log(err);
  }
});

We delete the first item that has the size field equal to 'large' .

Conclusion

We can manipulate MongoDB documents via models in with Mongoose.

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