Group Array of JavaScript Objects by Key or Property Value

group-objects-by-property-name.md

How to group an array of JavaScript objects by key or property value

I first came across this code on JamieMason's gist. Here I've tried to re-create it from scratch as I found their solution slightly hard to follow.

Implementation

function groupBy(key) {
  return function group(array) {
    return array.reduce((acc, obj) => {
      const property = obj[key];
      acc[property] = acc[property] || [];
      acc[property].push(obj);
      return acc;
    }, {});
  }
}

Usage

const dogs = [
  { name: 'Biscuit', age: '23', 'color': 'black '},
  { name: 'Diamond', age: '21', 'color': 'white '},
  { name: 'Oreo', age: '20', 'color': 'yellow '},
  { name: 'Zelda', age: '19', 'color': 'red'},
  { name: 'Snuggles', age: '23', 'color': 'red '},
  { name: 'Ron Burgandy', age: '23', 'color': 'black '},
];

const groupByAge = groupBy('age');
console.log(groupByAge(dogs));

Output

{
  '19': [ { name: 'Zelda', age: '19', color: 'red' } ],
  '20': [ { name: 'Oreo', age: '20', color: 'yellow ' } ],
  '21': [ { name: 'Diamond', age: '21', color: 'white ' } ],
  '23': [
    { name: 'Biscuit', age: '23', color: 'black ' },
    { name: 'Snuggles', age: '23', color: 'red ' },
    { name: 'Ron Burgandy', age: '23', color: 'black ' }
  ]
}

P.S. I'm aware that most dogs don't live to be 23 years old. RIP biscuit.