How to Merge Array of Objects by Property using Lodash?

Last Updated : 22 Aug, 2024

Merging an array of objects by property using Lodash is a common operation when you need to consolidate data that share a common identifier. For example, if you have a list of user objects and you want to combine them into a single object based on a unique property, Lodash provides useful functions to simplify this process.

Below are different approaches to merging objects in an array by a specific property using Lodash:

Table of Content

Using _.merge( ) and _.groupBy ( )
Using _.keyBy ( ) and _.assign ( )

Using _.merge( ) and _.groupBy ( )

In this approach, we first group the objects in the array based on a common property using _.groupBy ( ). Then, we merge the objects within each group using _.merge ( ). This method is useful when we have multiple objects that should be combined into one based on a shared key.

Syntax:

const groupedObjects = _.groupBy(array, 'property');
const mergedObjects = _.mapValues(groupedObjects, group => _.merge({}, ...group));

Example: This code groups an array of student objects by their id and merges the objects within each group into a single object, consolidating information for each student.

JavaScript

// Import lodash using CommonJS require
const _ = require('lodash');

const students = [
    { id: 1, name: 'Geek', grade: 'A' },
    { id: 2, name: 'Geekina', grade: 'B' },
    { id: 1, sports: 'Soccer' },
    { id: 2, sports: 'Basketball' }
];

// Group students by 'id'
const groupedStudents = _.groupBy(students, 'id');

// Merge objects within each group
const mergedStudents =
    _.mapValues(groupedStudents, group =>
        _.merge({}, ...group));

console.log(mergedStudents);

Output:

Using _.keyBy ( ) and _.assign ( )

In this approach, we first use _.keyBy ( ) to turn the array of objects into an object, where each key is the value of the specified property. Then, we use _.assign ( ) or _.merge ( ) to combine these objects. This method is efficient and works well when we want to quickly merge objects by a property.

Syntax:

const keyedObjects = _.keyBy(array, 'property');
const mergedObject = _.assign({}, keyedObjects);

Example: This code keys an array of student objects by their id and merges the keyed objects into a single object, consolidating the information for each student.

JavaScript

// Import lodash using CommonJS require
const _ = require('lodash');

const students = [
    { id: 1, name: 'Geek', grade: 'A' },
    { id: 2, name: 'Geekina', grade: 'B' },
    { id: 1, sports: 'Soccer' },
    { id: 2, sports: 'Basketball' }
];

// Key the students by 'id'
const keyedStudents = _.keyBy(students, 'id');

// Merge the keyed student objects
const mergedStudent = _.assign({}, keyedStudents);

console.log(mergedStudent);