Run results for: Object.keys ForEach vs for-in hasOwnProperty

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36

Browser: Chrome 84

Operating system: Mac OS X 10.15.6

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
A	958095.8 Ops/sec
B	1301429.0 Ops/sec
C	2006291.0 Ops/sec
D	2020194.0 Ops/sec

Script Preparation code:

// Declaring our Animal object
var Animal = function () {

    this.name = 'unknown';

    this.getName = function () {
        return this.name;
    }

    return this;
};

// Declaring our Dog object
var Dog = function () {

    // A private variable here        
    var private = 42;

    // overriding the name
    this.name = "Bello";

    // Implementing ".bark()"
    this.bark = function () {
        return 'MEOW';
    }  

    return this;
};


// Dog extends animal
Dog.prototype = new Animal();

// Creating an instance of Dog.
var obj = new Dog();

function iterateA() {
  var ret = "";
    
  for (var prop in obj) {
    if( obj.hasOwnProperty( prop ) ) {
      ret += obj[prop];
    } 
  }
    
  return ret;
}

function iterateB() {
  var ret = "";
    
  Object.keys(obj).forEach(function (prop) {
    ret += obj[prop];
  });

  return ret;
}

function iterateC() {
   var ret = "";

   for (var i = 0, keys = Object.keys(obj); i < keys.length; i++) {
       ret += obj[i];
   }

   return ret;
}

function iterateD() {
   var ret = "";

   for (var keys = Object.keys(obj), len = keys.length, i = 0; i < len; i++) {
       ret += obj[i];
   }

   return ret;
}

Tests:

A
var tmp = iterateA();
B
var tmp = iterateB();
C
var tmp = iterateC();
D
var tmp = iterateD();

Run results for: Object.keys ForEach vs for-in hasOwnProperty

Original source: https://jsperf.com/object-keys-foreach-vs-for-in-hasownproperty

A

B

C

D