using lodash .groupBy. how to add your own keys for grouped output?
You can do it like this in both Underscore and Lodash (3.x and 4.x).
var data = [{ "name": "jim", "color": "blue", "age": "22"}, { "name": "Sam", "color": "blue", "age": "33"}, { "name": "eddie", "color": "green", "age": "77"}];console.log( _.chain(data) // Group the elements of Array based on `color` property .groupBy("color") // `key` is group's name (color), `value` is the array of objects .map((value, key) => ({ color: key, users: value })) .value());<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>Original Answer
var result = _.chain(data) .groupBy("color") .pairs() .map(function(currentItem) { return _.object(_.zip(["color", "users"], currentItem)); }) .value();console.log(result);Note: Lodash 4.0 onwards, the .pairs function has been renamed to _.toPairs()
Isn't it this simple?
var result = _(data) .groupBy(x => x.color) .map((value, key) => ({color: key, users: value})) .value();
Highest voted answer uses Lodash _.chain function which is considered a bad practice now "Why using _.chain is a mistake."
Here is a fewliner that approaches the problem from functional programming perspective:
import tap from "lodash/fp/tap";import flow from "lodash/fp/flow";import groupBy from "lodash/fp/groupBy";const map = require('lodash/fp/map').convert({ 'cap': false });const result = flow( groupBy('color'), map((users, color) => ({color, users})), tap(console.log) )(input)Where input is an array that you want to convert.