How does Query.prototype.merge() works in Mongoose ?
The Query.prototype.merge() function is used to merge another Query or conditions object into the current query for which this function is used i.e this query. When a Query is passed, conditions, field selection and options are merged.
Syntax:
Query.prototype.merge()
Parameters: This function has one source parameter of Object/Query type.
Return Value: This function returns Query Object.
Mongoose Installation:
npm install mongoose
After installing the mongoose module, you can check your mongoose version in command prompt using the command.
npm mongoose --version
After that, you can just 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' );
useNewUrlParser: true ,
useCreateIndex: true ,
useUnifiedTopology: true
});
const User = mongoose.model( 'User' , {
name: { type: String },
age: { type: Number }
});
const query = User.find({age: { $gte:0 }})
console.log( "Before merge function" )
query.exec( function (err, res){
if (err) console.log(err)
else console.log(res)
});
setTimeout( function () {
query.merge({name: "Gourav" })
console.log( "After merge function" )
query.exec( function (err, res){
if (err) console.log(err)
else console.log(res)
});
}, 1000);
|
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Before merge function
[
{ _id: 5ebb9129a99bde77b2efb809, name: ‘Gourav’, age: 10, __v: 0 },
{ _id: 5ebc3669a99bde77b2efb9ba, name: ‘Lalit’, age: 25, __v: 0 },
{ _id: 5ebc367da99bde77b2efb9bf, name: ‘Piyush’, age: 5, __v: 0 },
{ _id: 5ebd345f5d2d8a3534b2f391, name: ‘Manish’, age: 34, __v: 0 }
]
After merge function
[ { _id: 5ebb9129a99bde77b2efb809, name: ‘Gourav’, age: 10, __v: 0 } ]
Example 2:
index.js
const express = require( 'express' );
const mongoose = require( 'mongoose' );
const app = express()
useNewUrlParser: true ,
useCreateIndex: true ,
useUnifiedTopology: true
});
const User = mongoose.model( 'User' , {
name: { type: String },
age: { type: Number }
});
const query = User.find({age: { $gte: 1}})
console.log( "Before merge function" )
query.exec( function (err, res){
if (err) console.log(err)
else console.log(res)
});
setTimeout( function () {
query.merge({name: "Gourav" })
console.log( "After merge function" )
query.exec( function (err, res){
if (err) console.log(err)
else console.log(res)
});
}, 1001);
app.listen(3000, function (error ) {
if (error) console.log(error)
console.log( "Server listening on PORT 3000" )
});
|
The project structure will look like this:
Run index.js file using below command:
node index.js
Output:
Before merge function
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 },
{ _id: 5ebd345f5d2d8a3534b2f391, name: ‘Manish’, age: 34, __v: 0 }
]
After merge function
[ { _id: 5ebb9129a99bde77b2efb809, name: ‘Gourav’, age: 10, __v: 0 }
Reference: https://mongoosejs.com/docs/api/query.html#query_Query-merge
Last Updated :
12 Mar, 2021
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