Benchmark: getOwnPropertyNames vs Object.keys

Script Preparation code:

var obj = {
  $props : ['a','b','c'],
  a:1,
  b:2,
  c:3
}

Tests:

getOwnPropertyNames
const arr = Object.keys(obj); let n = 0; for (let i = 0; i < arr.length; i++) { const k = arr[i]; if (k.charAt(0) == '$') continue; n++; }
for ... in
let n = 0; for (const k in obj) { if (k.charAt(0) == '$') continue; n++; }

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

for ... in

27.7M/s

getOwnPropertyNames

17.4M/s

Fastest: for ... in (1.6x faster)

View exact numbers

✓ for ... in: 27,688,008 ops/sec
• getOwnPropertyNames: 17,357,724 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getOwnPropertyNames
for ... in

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/137.0.0.0 Safari/537.36

Browser/OS: Chrome 137 on Windows

View result in a separate tab

for ... in

62.8M/s

getOwnPropertyNames

46.5M/s

View exact numbers

Test name	Executions per second
✓ for ... in	62,834,376 Ops/sec
getOwnPropertyNames	46,521,324 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 benchmark and its test cases.

**What is being tested?**

The benchmark is comparing two approaches to iterate over an object's property names:

1. `getOwnPropertyNames` (also known as the "object property iterator" in ECMAScript): This method returns a static view of an object's own enumerable property names.
2. The `for ... in` loop: This syntax allows iterating over an object's properties, including those that are not enumerable.

**Options compared**

The two approaches being tested are:

1. **getOwnPropertyNames**: Using the `Object.keys()` method to get an array of property names and then iterating over it.
2. **for ... in**: Using a traditional `for` loop with the `in` keyword to iterate over the object's properties.

**Pros and cons**

**getOwnPropertyNames**:

Pros:

* More efficient, as it avoids the overhead of checking each property's enumerable status.
* Can be faster for large objects.

Cons:

* Requires an additional method call (`Object.keys()`), which might incur additional overhead.
* May not work correctly in older browsers that do not support `Object.keys()`.
* Returns only own enumerable properties (not inherited ones).

**for ... in**:

Pros:

* Simple and widely supported, as it's a built-in syntax.
* Works correctly with all objects, including inherited ones.

Cons:

* Slower due to the overhead of checking each property's enumerable status.
* Can be slower for large objects, as it has to iterate over all properties.

**Library/Functionality Used**

None of the test cases use any external libraries or functions besides the built-in `Object.keys()` method and the JavaScript `for` loop syntax.

**Special JS Features/Syntax**

The only special feature used in these test cases is the `in` keyword in the `for ... in` loop, which is a part of the traditional `for` loop syntax. This keyword allows iterating over an object's properties.

**Alternatives**

Other alternatives for iterating over an object's property names could be:

* Using the `Object.getOwnPropertyNames()` method (which returns only own enumerable and non-writable properties).
* Using a library like Lodash or Underscore.js, which provide utility functions for working with objects.
* Using a custom implementation, such as using a recursive function to iterate over an object's properties.

However, these alternatives are not tested in this benchmark, and the results may vary depending on the specific use case and performance requirements.

getOwnPropertyNames vs Object.keys (version: 0)

yeah

Comparing performance of: `getOwnPropertyNames vs for ... in`

Created: 7 years ago by: Guest

Go to the latest result

getOwnPropertyNames

for ... in

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

getOwnPropertyNames vs Object.keys (version: 0)

yeah

Comparing performance of: getOwnPropertyNames vs for ... in

Created: 7 years ago by: Guest

Go to the latest result

getOwnPropertyNames

for ... in

Historical Performance Data aggregated from 10 community runs

Desktop Results:

Chrome 10 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

Comparing performance of: `getOwnPropertyNames vs for ... in`