Run results for: reduce vs foreach

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_0_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.198 Safari/537.36

Browser: Chrome 86

Operating system: Mac OS X 11.0.0

Device Platform: Desktop

Date tested: 3 years ago

Test name	Executions per second
reduce	34274.9 Ops/sec
foreach	41674.2 Ops/sec

Script Preparation code:

var data = [
  {id: 1, name: 'test1'},
  {id: 2, name: 'test2'},
  {id: 3, name: 'test3'},
  {id: 4, name: 'test4'},
  {id: 5, name: 'test5'},
  {id: 6, name: 'test6'},
  {id: 7, name: 'test7'},
  {id: 8, name: 'test8'},
  {id: 9, name: 'test9'},
  {id: 10, name: 'test10'},
  {id: 11, name: 'test11'},
  {id: 12, name: 'test12'},
  {id: 13, name: 'test13'},
  {id: 14, name: 'test14'},
  {id: 15, name: 'test15'},
  {id: 16, name: 'test16'},
  {id: 17, name: 'test17'},
  {id: 18, name: 'test18'},
  {id: 19, name: 'test19'},
];

Tests:

reduce
var flattened = data.reduce((entities, item) => { return { ...entities, [item.id]: item } }, {}); console.log(flattened);
foreach
var flattened = {}; data.forEach((item) => { flattened[item.id] = item; }); console.log(flattened);