How does Query.prototype.cursor() work in Mongoose?
The Query.prototype.cursor() function returns a wrapper around a MongoDB driver cursor. And this function triggers the pre find hooks, not the post find hooks.
Syntax:
Query.prototype.cursor()
Parameters: This function has one optional parameter i.e. transform which is an optional function which accepts a mongoose document.
Return Value: This function returns QueryCursor Object.
Installing mongoose :
npm install mongoose
After installing the mongoose module, you can check your mongoose version in command prompt using the command.
npm mongoose --version
Now, create a folder and add a file for example, index.js as shown below.
Database: The sample database used here is shown below:
Example 1:
index.js
const mongoose = require( 'mongoose' ); // Database connection mongoose.connect( 'mongodb://127.0.0.1:27017/w3wiki' , { useNewUrlParser: true , useCreateIndex: true , useUnifiedTopology: true }); // User model const User = mongoose.model( 'User' , { name: { type: String }, age: { type: Number } }); var cursor = User.find({}).cursor(); cursor.next( function (error, doc) { console.log(doc); }); |
Steps to run the program:
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
{ _id: 5ebb9129a99bde77b2efb809, name: ‘Gourav’, age: 10, __v: 0 }
Example 2:
index.js
const express = require( 'express' ); const mongoose = require( 'mongoose' ); const app = express() // Database connection mongoose.connect( 'mongodb://127.0.0.1:27017/w3wiki' , { useNewUrlParser: true , useCreateIndex: true , useUnifiedTopology: true }); // User model const User = mongoose.model( 'User' , { name: { type: String }, age: { type: Number } }); var cursor = User.find({}).cursor(); //first call cursor.next( function (error, doc) { console.log(doc); }); //second call cursor.next( function (error, doc) { console.log(doc); }); //third call cursor.next( function (error, doc) { console.log(doc); }); app.listen(3000, function (error ) { if (error) console.log(error) console.log( "Server listening on PORT 3000" ) }); |
Steps to run the program:
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Server listening on PORT 3000
{ _id: 5ebb9129a99bde77b2efb809, name: ‘Gourav’, age: 10, __v: 0 }
{ _id: 5ebc3669a99bde77b2efb9ba, name: ‘Lalit’, age: 25, __v: 0 }
{ _id: 5ebc367da99bde77b2efb9bf, name: ‘Piyush’, age: 5, __v: 0 }
Reference:
https://mongoosejs.com/docs/api/query.html#query_Query-cursor