Benchmark: getOwnPropertyNames vs loop vs cached property names

Script Preparation code:

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

Tests:

getOwnPropertyNames
var ks = Object.getOwnPropertyNames(obj); var n = 0; for (var i = 0; i < ks.length; i++) { var k = obj[ks[i]]; if (k.charAt(0) == '$') continue; n++; }
Cached property names
var ks = obj['$names']; var n = 0; for (var i = 0; i < ks.length; i++) { var k = obj[ks[i]]; n++; }
for in
var n = 0; for (var 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
getOwnPropertyNames
Cached property names
for in

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 8 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36

Browser/OS: Chrome 53 on Mac OS X 10.10.5

View result in a separate tab

Test name	Executions per second
getOwnPropertyNames	0.0 Ops/sec
Cached property names	2581982.0 Ops/sec
for in	4346397.5 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months 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 designed to compare three approaches for iterating over an object's properties:

1. **`Object.getOwnPropertyNames()`**: This method returns an array of strings representing the names of all properties (including inherited ones) that are directly accessible on an object.
2. **Cached property names**: In this approach, we assume that some libraries or frameworks provide a cached list of property names for an object, which is then used to iterate over the properties.
3. **`for...in` loop with filtering**: This approach uses the `for...in` loop to iterate over all properties of an object and skips any properties whose name starts with a dollar sign (`$`).

**Options comparison**

The three approaches have different pros and cons:

* **`Object.getOwnPropertyNames()`**:
	+ Pros: Simple, straightforward, and efficient.
	+ Cons: May include inherited properties, which can be slow to iterate over for large objects.
* **Cached property names**:
	+ Pros: Can be faster than `getOwnPropertyNames()` if the cached list is already available.
	+ Cons: Assumes that a library or framework provides the cached list, which may not always be the case.
	+ Pros (if implemented correctly): Avoids iterating over inherited properties and can be optimized for large objects.
	+ Cons (if implemented incorrectly): May still include inherited properties or introduce additional overhead.
* **`for...in` loop with filtering**:
	+ Pros: Flexible, as it allows filtering out properties based on their names.
	+ Cons: Can be slower than `getOwnPropertyNames()` and cached property names if not optimized.

The `for...in` loop approach is currently the fastest, but this might change depending on the specific implementation and browser optimizations.

**Library considerations**

The benchmark uses the `Object.getOwnPropertyNames()` method, which is a standard JavaScript method. No external libraries are required for these test cases.

**Special JS features or syntax**

There are no special JavaScript features or syntax used in these test cases.

**Other alternatives**

If you wanted to include other approaches in your benchmark, some alternative methods for iterating over an object's properties could be:

* Using `Object.keys()` (which returns only own enumerable properties) and then filtering out properties whose names start with a dollar sign.
* Using a custom iteration function or a recursive approach.
* Comparing performance of using `for...in`, `for...of` (if supported), or other iteration methods.

Keep in mind that each alternative method has its pros and cons, and the best choice depends on your specific use case and requirements.

Related benchmarks:

getOwnPropertyNames vs loop vs cached property names (version: 0)

Comparing performance of: getOwnPropertyNames vs Cached property names vs for in

Created: 8 years ago by: Guest

Jump to the latest result

getOwnPropertyNames

Cached property names

for in

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):