Mongoose SchemaType.prototype.transform() API
Mongoose is a MongoDB object modeling and handling for a node.js environment. Mongoose SchemaType transform is a SchemaType method that allows us to transform or manipulate a path when converting a document into JSON. Mongoose uses the current value of the path as a parameter for the method. Let’s understand more about this with some examples.
Creating node application And Installing Mongoose:
Step 1: Create a node application using the following command:
mkdir folder_name cd folder_name npm init -y touch main.js
Step 2: After creating the ReactJS application, Install the required module using the following command:
npm install mongoose
Project Structure: It will look like the following.
Example 1: In this example, we will create a transform function that will give us the year of the data stored in a path.
Filename: main.js
Javascript
const mongoose = require( 'mongoose' ) // Database connection mongoose.connect( 'mongodb://localhost:27017/query-helpers' , { dbName: 'event_db' , useNewUrlParser: true , useUnifiedTopology: true }, err => err ? console.log(err) : console.log( 'Connected to database' )); const personSchema = new mongoose.Schema({ date: { type: Date, transform: v => v.getFullYear() } }); const Person = mongoose.model( 'Person' , personSchema); const person = new Person({ date: new Date() }); console.log(person.toJSON().date); |
Step to Run Application: Run the application using the following command from the root directory of the project:
node main.js
Output:
Example 2: In this example, we will create a transform function that will give us the full name of a person from an Array of first names and Last names.
Filename: main.js
Javascript
const mongoose = require( 'mongoose' ) // Database connection mongoose.connect( 'mongodb://localhost:27017/query-helpers' , { dbName: 'event_db' , useNewUrlParser: true , useUnifiedTopology: true }, err => err ? console.log(err) : console.log( 'Connected to database' )); const personSchema = new mongoose.Schema({ name: { type: Array, transform: v => v.join( ' ' ) } }); const Person = mongoose.model( 'Person' , personSchema); const person = new Person({ name: [ 'John' , 'Doe' ] }); console.log(person.toJSON().name); |
Step to Run Application: Run the application using the following command from the root directory of the project:
node main.js
Output:
Reference: https://mongoosejs.com/docs/api/schematype.html#schematype_SchemaType-transform
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