Run results for: Object iteration vs Map iteration

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:128.0) Gecko/20100101 Firefox/128.0

Browser: Firefox 128

Operating system: Mac OS X 10.15

Device Platform: Desktop

Date tested: 2 years ago

Object - for in

8.9M/s

Map - forEach

6.1M/s

Map - for of kv

2.5M/s

Object.entries() - for of kv

2.0M/s

Object.entries() - forEach

226K/s

View exact numbers

Test name	Executions per second
✓ Object - for in	8,908,500 Ops/sec
Map - forEach	6,099,721 Ops/sec
Map - for of kv	2,451,102 Ops/sec
Object.entries() - for of kv	2,024,773 Ops/sec
Object.entries() - forEach	226,349 Ops/sec

Script Preparation code:

var obj = {
  a: 1,
  b: 2,
  c: 3,
  d: 4,
  e: 5,
  f: 6,
  g: 7,
  h: 8,
  i: 9,
  j: 10,
  k: 11,
  l: 12,
  m: 13,
  n: 14,
  o: 15,
  p: 16,
  q: 17,
  r: 18,
  s: 19,
  t: 20,
  u: 21,
  v: 22,
  w: 23,
  x: 24,
  y: 25,
  z: 26
};
var map = new Map(Object.entries(obj));

Tests:

Map - for of kv
let total = 0; for (const [key, value] of map) { total += value; }
Map - forEach
let total = 0; map.forEach(function(value, key) { total += value; });
Object.entries() - for of kv
let total = 0; for (const [key, value] of Object.entries(obj)) { total += value; }
Object.entries() - forEach
let total = 0; Object.entries(obj).forEach(function(value, key) { total += value; });
Object - for in
let total = 0; for (const key in obj) { total += obj[key]; }