Suppose, we have an array of objects containing data about some cars like this −
const arr = [ { 'make': 'audi', 'model': 'r8', 'year': '2012' }, { 'make': 'audi', 'model': 'rs5', 'year': '2013' }, { 'make': 'ford', 'model': 'mustang', 'year': '2012' }, { 'make': 'ford', 'model': 'fusion', 'year': '2015' }, { 'make': 'kia', 'model': 'optima', 'year': '2012' }, ];
We are required to write a JavaScript function that takes in one such array of objects. The function should then group the objects together based on their 'make' property.
Output
Therefore, the output should look something like this −
const output = { 'audi': [ { 'model': 'r8', 'year': '2012' }, { 'model': 'rs5', 'year': '2013' }, ], 'ford': [ { 'model': 'mustang', 'year': '2012' }, { 'model': 'fusion', 'year': '2015' } ], 'kia': [ { 'model': 'optima', 'year': '2012' } ] };
Example
The code for this will be −
const arr = [ { 'make': 'audi', 'model': 'r8', 'year': '2012' }, { 'make': 'audi', 'model': 'rs5', 'year': '2013' }, { 'make': 'ford', 'model': 'mustang', 'year': '2012' }, { 'make': 'ford', 'model': 'fusion', 'year': '2015' }, { 'make': 'kia', 'model': 'optima', 'year': '2012' }, ]; const groupByMake = (arr = []) => { let result = []; result = arr.reduce((r, a) => { r[a.make] = r[a.make] || []; r[a.make].push(a); return r; }, Object.create(null)); return result; }; console.log(groupByMake(arr));
Output
And the output in the console will be −
{ audi: [ { make: 'audi', model: 'r8', year: '2012' }, { make: 'audi', model: 'rs5', year: '2013' } ], ford: [ { make: 'ford', model: 'mustang', year: '2012' }, { make: 'ford', model: 'fusion', year: '2015' } ], kia: [ { make: 'kia', model: 'optima', year: '2012' } ] }