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 = 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 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36

Browser/OS: Chrome 53 on Windows 8.1

View result in a separate tab

Test name	Executions per second
getOwnPropertyNames	1544487.9 Ops/sec
Cached property names	2499515.5 Ops/sec
for in	4462775.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Measuring the performance of different approaches to iterate over an object's properties is crucial in understanding the underlying mechanics of JavaScript's `for...in` loop, `Object.getOwnPropertyNames()`, and accessing properties via arrays.

**Options being compared:**

1. **getOwnPropertyNames()**: This method returns an array containing all the property names of an object.
2. **Loop with manual property iteration**: This involves looping through the `Object.getOwnPropertyNames()` result and checking if each property name starts with a `$` (indicating it's not a special property). If it does, it skips that iteration.
3. **Cached property names**: This approach uses the `$names` array directly to iterate over its elements, accessing the corresponding properties via bracket notation (`obj[ks[i]]`).

**Pros and Cons of each approach:**

1. **getOwnPropertyNames()**:
	* Pros:
		+ Efficient, as it only requires one pass through the object's properties.
		+ Reduces overhead associated with manual property iteration.
	* Cons:
		+ May be slower due to the extra function call and array access.
2. **Loop with manual property iteration**:
	* Pros:
		+ Provides explicit control over the iteration process, allowing for potential optimizations or handling of special properties.
	* Cons:
		+ Requires more CPU cycles due to the additional loop overhead.
3. **Cached property names**:
	* Pros:
		+ Similar performance characteristics to `getOwnPropertyNames()`, as it leverages the optimized array access.
	* Cons:
		+ Only works if `$names` is an array, which might not be the case for all objects.

**Library usage:**

None of the benchmark cases explicitly use a library. However, some JavaScript engines (like V8 in Chrome) provide built-in optimizations and features that can influence performance.

**Special JS feature or syntax:**

There are no explicit special features or syntaxes mentioned in the benchmark definition. The `$names` array is used as an array literal, which is a standard JavaScript syntax.

**Other considerations:**

1. **Browser variability**: Different browsers might exhibit varying performance due to their respective engines and optimization strategies.
2. **Object structure**: The specific object being tested can impact performance, especially if it contains many properties or has complex internal structures.

**Alternative approaches:**

Some possible alternative approaches for iterating over an object's properties include:

1. Using a `for...in` loop with the `hasOwnProperty()` method to filter out special properties.
2. Utilizing the `Object.keys()` method, which returns an array of property names.
3. Leveraging modern JavaScript features like `for...of` loops or `Map`/`Set` objects for iteration.

However, these alternatives are not explicitly tested in this benchmark case.

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):