Run details:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/95.0.4638.54 Safari/537.36
Chrome 95
Mac OS X 10.15.7
Desktop
3 years ago
Test name Executions per second
for in 2.0 Ops/sec
object keys 1.1 Ops/sec
for in object keys 15297.4 Ops/sec
Script Preparation code:
AخA
 
var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1
};
Tests:
  • for in

     
    for (var i=10000; i > 0; i--) {
      for (var key in obj) {
          console.log(key); 
      }
    }
  • object keys

     
    for (var i=10000; i > 0; i--) {
      Object.keys(obj).forEach(key => console.log(key));
    }
  • for in object keys

     
    for (var i = 0, keys = Object.keys(obj); i < keys.length; i++) {
        console.log(keys[i])
    }