Run results for: lodash/partitionBy vs native reduce

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/123.0.0.0 Safari/537.36

Browser: Chrome 123

Operating system: Mac OS X 10.15.7

Device Platform: Desktop

Date tested: 2 years ago

Test name	Executions per second
_.partitionBy(data, (v) => v.name);	0.0 Ops/sec
partitionBy with native reduce	395742.8 Ops/sec
partitionBy with forEach	3115273.5 Ops/sec
partitionBy with for loop	4565321.5 Ops/sec

HTML Preparation code:

<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js'></script>

Script Preparation code:

var data = [
  { name: 'pi', value: 3.14 },
  { name: 'hundred', value: 100 },
  { name: 'truthy', value: true },
  { name: 'falsy', value: false },
  { name: 'estring', value: '2.71828' },
];

var partitionBy = (arr, key) => Object.values(arr.reduce((acc, item) => {
    var _a;
    return (Object.assign(Object.assign({}, acc), { [String(item[key])]: [...((_a = acc[String(item[key])]) !== null && _a !== void 0 ? _a : []), item] }));
}, {}));

var partitionByForEach = (array, fn) => {
  var acc = {};
  _.forEach(array, (value) => {
    acc[fn(value)] = value;
  });
  return Object.values(acc);
};

var partitionByForLoop = (array, fn) => {
  var acc = {};
  for (let i = 0; i < array.length; i++) {
    acc[fn(array[i])] = array[i];
  }
  return Object.values(acc);
};

Tests:

_.partitionBy(data, (v) => v.name);
_.partitionBy(data, (v) => v.name);
partitionBy with native reduce
partitionBy(data, (v) => v.name);
partitionBy with forEach
partitionByForEach(data, (v) => v.name);
partitionBy with for loop
partitionByForLoop(data, (v) => v.name);

Run results for: lodash/partitionBy vs native reduce

_.partitionBy(data, (v) => v.name);

partitionBy with native reduce

partitionBy with forEach

partitionBy with for loop