Mongoose Query() Function
Last Updated :
10 Sep, 2020
The Query constructor is used for building the queries. So the user does not need to instantiate a Query directly. The `query` is an instance of `Query`.
Syntax:
Query()
Parameters: This function has optional parameters like model, condition, collection and options.
Return Value: This function returns Query object.
Installation of mongoose module:
npm install mongoose
- After installing the mongoose module, you can check your mongoose version in command prompt using the command.
npm version mongoose
- After that, you can just create a folder and add a file for example, index.js as shown below.
Example 1: Filename: index.js
javascript
const express = require('express');
const mongoose = require('mongoose');
const app = express()
// Database connection
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', {
useNewUrlParser: true,
useCreateIndex: true,
useUnifiedTopology: true
});
// User model
const User = mongoose.model('User', {
name: { type: String },
age: { type: Number }
});
const query = new mongoose.Query();
console.log(query);
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:
Query {
_mongooseOptions: {},
_transforms: [],
_hooks: Kareem { _pres: Map {}, _posts: Map {} },
_executionCount: 0,
op: undefined,
options: {},
_conditions: {},
_fields: undefined,
_update: undefined,
_path: undefined,
_distinct: undefined,
_collection: undefined,
_traceFunction: undefined,
'$useProjection': true
}
Server listening on PORT 3000
Example 2: Filename: index.js
javascript
const mongoose = require('mongoose');
// Database connection
mongoose.connect('mongodb://127.0.0.1:27017/geeksforgeeks', {
useNewUrlParser: true,
useCreateIndex: true,
useUnifiedTopology: true
});
// User model
const User = mongoose.model('User', {
name: { type: String },
age: { type: Number }
});
const query = new mongoose.Query();
query.collection(User.collection);
console.log(query);
Steps to run the program:
- The project structure will look like this:
- Run index.js file using below command:
node index.js
Output:
Query {
_mongooseOptions: {},
_transforms: [],
_hooks: Kareem { _pres: Map {}, _posts: Map {} },
_executionCount: 0,
op: undefined,
options: {},
_conditions: {},
_fields: undefined,
_update: undefined,
_path: undefined,
_distinct: undefined,
_collection: NodeCollection {
collection: NativeCollection {
collection: null,
Promise: [Function: Promise],
_closed: false,
opts: [Object],
name: 'users',
collectionName: 'users',
conn: [NativeConnection],
queue: [],
buffer: true,
emitter: [EventEmitter]
},
collectionName: 'users'
},
_traceFunction: undefined,
'$useProjection': true
}
Reference: https://mongoosejs.com/docs/api/query.html
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