Collect.js mapToGroups() Method

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The mapToGroups() method is used to iterate through the collection elements and passes each value of collection into the given callback function.

Syntax:

collect(array).mapToGroups(callback)

Parameters: The collect() method takes one argument that is converted into the collection and then mapToGroups() method is applied on it. The mapToGroups() method holds the callback function as a parameter.

Return Value: This method returns the collection elements according to given callback.

Below example illustrate the mapToGroups() method in collect.js:

Example 1:

Javascript

const collect = require('collect.js'); 
  
let obj = [{ 
    name: 'Ashok', 
    score: 75 
}, 
{ 
    name: 'Rakesh', 
    score: 86 
}, 
{ 
    name: 'Rajesh', 
    score: 56 
}, 
{ 
    name: 'Rakesh', 
    score: 98 
}]; 
  
const collection = collect(obj); 
  
const sequence = collection.mapToGroups( 
    (element) => [element.name, element.score]) 
  
console.log(sequence.all());

Output:

{ Ashok: [ 75 ], Rakesh: [ 86, 98 ], Rajesh: [ 56 ] }

Example 2:

Javascript

const collect = require('collect.js'); 
  
let obj = [ 
    { 
        name: 'Rahul', 
        dob: '25-10-96', 
    }, 
    { 
        name: 'Aditya', 
        dob: '25-10-96', 
    }, 
    { 
        name: 'Abhishek', 
        dob: '16-08-94', 
    }, 
    { 
        name: 'Rahul', 
        dob: '25-10-96', 
    }, 
]; 
  
const collection = collect(obj); 
  
const sequence = collection.mapToGroups( 
    (element) => [element.dob, element.name]) 
  
console.log(sequence.all());

Output:

{
  '25-10-96': [ 'Rahul', 'Aditya', 'Rahul' ],
  '16-08-94': [ 'Abhishek' ]
}

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