Lodash:如何使用多个嵌套属性进行分组？

const _ = require('lodash');

const data = [
  { name: 'Alice', age: 25, city: 'New York' },
  { name: 'Bob', age: 30, city: 'San Francisco' },
  { name: 'Charlie', age: 35, city: 'New York' },
  { name: 'Dave', age: 40, city: 'San Francisco' }
];

const groupedData = _.groupBy(data, item => `${item.city}-${item.age}`);

console.log(groupedData);

{
  'New York-25': [ { name: 'Alice', age: 25, city: 'New York' } ],
  'San Francisco-30': [ { name: 'Bob', age: 30, city: 'San Francisco' } ],
  'New York-35': [ { name: 'Charlie', age: 35, city: 'New York' } ],
  'San Francisco-40': [ { name: 'Dave', age: 40, city: 'San Francisco' } ]
}