Benchmark: for-in with hasOwnProperty() vs object.keys

Script Preparation code:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
for-in
Object.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36

Browser/OS: Chrome 133 on Windows

View result in a separate tab

Test name	Executions per second
for-in	3.4 Ops/sec
Object.keys	2.8 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark definition and test cases.

**What is being tested?**

The benchmark measures the performance of two different approaches for iterating over an object:

1. **for-in**: This approach uses the `in` keyword to iterate over the object's properties, and then checks if each property is a direct property using the `hasOwnProperty()` method.
2. **Object.keys**: This approach uses the `Object.keys()` function to get an array of the object's property keys, which can be iterated over directly.

**Options compared**

The two approaches are being compared:

* **for-in with hasOwnProperty()**: This is the traditional way of iterating over an object's properties in JavaScript.
* **Object.keys**: A more modern and efficient approach to get an array of property keys.

**Pros and Cons of each approach:**

1. **for-in with hasOwnProperty()**:
	* Pros:
		+ Simple and easy to understand.
		+ Works well for small objects.
	* Cons:
		+ Can be slower due to the additional overhead of checking if a property is a direct property using `hasOwnProperty()`.
2. **Object.keys**:
	* Pros:
		+ Faster and more efficient.
		+ More concise and expressive code.
	* Cons:
		+ Requires the use of a modern browser or Node.js, as it was introduced in ECMAScript 2015.

**Library and syntax used**

None, this benchmark is using only built-in JavaScript features and libraries.

**Special JS feature or syntax**

No special features or syntax are being tested in this benchmark. The focus is on comparing the performance of two simple approaches to iterate over an object's properties.

**Other alternatives**

If you want to use other methods to iterate over an object's properties, some alternatives could be:

* Using a `for` loop with array-like indices (e.g., `obj[0]`, `obj[1]`, etc.)
* Using a library like Lodash or Ramda for functional programming approaches
* Using the `entries()` method and iterating over it directly

However, these alternatives may not be relevant to this specific benchmark, which is focused on comparing two basic approaches using built-in JavaScript features.

Related benchmarks:

for-in with hasOwnProperty() vs object.keys (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 6 years ago by: Guest

Jump to the latest result

for-in

Object.keys

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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