Benchmark: getOwnPropertyNames() vs Object.keys() vs for ... in

Script Preparation code:

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

Tests:

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

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Object.keys()
getOwnPropertyNames()
for ... in loop

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Object.keys()	9906305.0 Ops/sec
getOwnPropertyNames()	9410627.0 Ops/sec
for ... in loop	26696090.0 Ops/sec

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):

LLMs can make mistakes. Check important info.

This benchmark compares three methods for extracting property names from a JavaScript object:

* **`Object.keys(obj)`:** This method returns an array containing the names of all enumerable properties on an object.  It's a common and straightforward way to get property names. 
   * **Pros:** Easy to understand and use, widely supported.
   * **Cons:** Doesn't include inherited properties (those from the prototype chain), can be slower than `getOwnPropertyNames()` for large objects.

* **`Object.getOwnPropertyNames(obj)`:** This method returns an array containing the names of all own properties on an object, including non-enumerable ones. 
   * **Pros:** More comprehensive as it includes inherited properties. Generally faster than `Object.keys()`.
   * **Cons:**  More complex syntax than `Object.keys()`.

* **`for ... in loop`:** This classic iteration method loops through the enumerable properties of an object and allows direct access to their names. 
   * **Pros:** Fine-grained control over the iteration process, can be optimized for specific use cases.
   * **Cons:** Can be less efficient than `Object.keys()` or `getOwnPropertyNames()`, more verbose syntax.

**Considerations:**

* **Performance:**  The benchmark results show that `for ... in` performs best in this particular case (on a Mac with Chrome 119). However, performance can vary significantly depending on factors like the size of the object, the browser engine, and the specific implementation details.
* **Accuracy:** Do you need to include inherited properties?  If not, `Object.keys()` might suffice. If you need all own properties, even non-enumerable ones, then `getOwnPropertyNames()` is preferable.

**Alternatives:**

There are a few other ways to extract property names from JavaScript objects:
* **Symbol Properties:** These properties can be accessed using `Object.getOwnPropertySymbols(obj)`. This method returns an array of symbols representing the symbol properties of an object.

Let me know if you have any more questions!

Related benchmarks:

getOwnPropertyNames() vs Object.keys() vs for ... in (version: 0)

Comparing performance of: Object.keys() vs getOwnPropertyNames() vs for ... in loop

Created: 2 years ago by: Guest

Jump to the latest result

Object.keys()

getOwnPropertyNames()

for ... in loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gemma2:9b, generated one year ago):