Skip to content

Instantly share code, notes, and snippets.

Embed
What would you like to do?
Group Array of JavaScript Objects by Key or Property Value

Group Array of JavaScript Objects by Keys or Property Values

This fork of JamieMason's implementation changes the key parameter to be an array of keys instead of just a single key. This makes it possible to group by multiple properties instead of just one.

Implementation

const groupBy = keys => array =>
  array.reduce((objectsByKeyValue, obj) => {
    const value = keys.map(key => obj[key]).join('-');
    objectsByKeyValue[value] = (objectsByKeyValue[value] || []).concat(obj);
    return objectsByKeyValue;
  }, {});

Usage

const cars = [
  { brand: 'Audi', produced: '2016', color: 'black' },
  { brand: 'Audi', produced: '2017', color: 'white' },
  { brand: 'Ford', produced: '2016', color: 'red' },
  { brand: 'Ford', produced: '2016', color: 'white' },
  { brand: 'Peugot', produced: '2018', color: 'white' }
];

const groupByBrand = groupBy(['brand']);
const groupByColor = groupBy(['color']);
const groupByBrandAndYear = groupBy(['brand', 'produced']);

console.log(
  JSON.stringify({
    carsByBrand: groupByBrand(cars),
    carsByColor: groupByColor(cars),
    carsByBrandAndYear: groupByBrandAndYear(cars)
  }, null, 2)
);

Output

{
  "carsByBrand": {
    "Audi": [
      {
        "brand": "Audi",
        "produced": "2016",
        "color": "black"
      },
      {
        "brand": "Audi",
        "produced": "2017",
        "color": "white"
      }
    ],
    "Ford": [
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "red"
      },
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "white"
      }
    ],
    "Peugot": [
      {
        "brand": "Peugot",
        "produced": "2018",
        "color": "white"
      }
    ]
  },
  "carsByColor": {
    "black": [
      {
        "brand": "Audi",
        "produced": "2016",
        "color": "black"
      }
    ],
    "white": [
      {
        "brand": "Audi",
        "produced": "2017",
        "color": "white"
      },
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "white"
      },
      {
        "brand": "Peugot",
        "produced": "2018",
        "color": "white"
      }
    ],
    "red": [
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "red"
      }
    ]
  },
  "carsByBrandAndYear": {
    "Audi-2016": [
      {
        "brand": "Audi",
        "produced": "2016",
        "color": "black"
      }
    ],
    "Audi-2017": [
      {
        "brand": "Audi",
        "produced": "2017",
        "color": "white"
      }
    ],
    "Ford-2016": [
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "red"
      },
      {
        "brand": "Ford",
        "produced": "2016",
        "color": "white"
      }
    ],
    "Peugot-2018": [
      {
        "brand": "Peugot",
        "produced": "2018",
        "color": "white"
      }
    ]
  }
}

See playcode.io for example.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
You can’t perform that action at this time.