Benchmark: Object length, Object Keys vs for loop

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 total = 0;
    
  for (var prop in obj) {
      total++;
  }
    
  return total;
}

function iterateB() {
  return Object.keys(obj).length;
}

Tests:

A
var tmp = iterateA();
B
var tmp = iterateB();

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
A
B

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/104.0.0.0 Safari/537.36

Browser/OS: Chrome 104 on Linux

View result in a separate tab

Test name	Executions per second
A	3440380.8 Ops/sec
B	4122543.8 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

I'll explain the provided benchmark and its options.

**Benchmark Overview**

The benchmark is designed to compare the performance of two approaches for iterating over an object's properties: using a `for...in` loop (approach A) versus using the `Object.keys()` method (approach B).

**Approaches Compared**

1. **For-in Loop (Approach A)**:
	* This approach iterates over the object's properties using a `for...in` loop, which includes inherited properties.
	* The loop increments a counter (`total`) for each property encountered.
2. **Object.keys() Method (Approach B)**:
	* This approach returns an array of the object's own enumerable property names using the `Object.keys()` method.
	* The length of this array is then returned, effectively counting the number of properties.

**Pros and Cons**

* **For-in Loop (Approach A)**
	+ Pros: can handle nested objects, can be used with `forEach` or other iteration methods.
	+ Cons: includes inherited properties, which may not be desirable in all cases. Also, it increments a counter (`total`) unnecessarily, adding overhead.
* **Object.keys() Method (Approach B)**
	+ Pros: faster and more efficient than the `for-in` loop, as it only counts own enumerable property names.
	+ Cons: does not include inherited properties, which may be desirable in some cases. Also, it creates an array of property names, which can be memory-intensive.

**Library Used**

In this benchmark, no libraries are explicitly mentioned. However, the `Animal` and `Dog` objects are custom classes that extend a basic object structure. The `getgetName()` method is also part of these objects, suggesting some level of object-oriented programming (OOP) complexity.

**Special JS Features/Syntax**

There is no explicit mention of any special JavaScript features or syntax in this benchmark. However, the use of OOP concepts like classes, inheritance (`Dog.prototype = new Animal()`), and custom methods (`getName()` and `bark()`) are examples of advanced JavaScript programming techniques.

**Alternatives**

Other alternatives for iterating over an object's properties include:

1. Using a simple `for` loop with the `in` keyword (e.g., `for (var prop in obj) { ... }`).
2. Using a `forEach()` method (e.g., `obj.forEach(function() { ... })`).
3. Using a library like Lodash or Underscore.js, which provide optimized methods for iterating over objects.

Overall, the benchmark is designed to compare the performance of two approaches for iterating over an object's properties in JavaScript.

Related benchmarks:

Object length, Object Keys vs for loop (version: 0)

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

Comparing performance of: A vs B

Created: 2 years ago by: Guest

Jump to the latest result

A

B

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):