Benchmark: for-in vs object.keybepb

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) { console.log(key); } }
Object.keys
for (var i=10000; i > 0; i--) { for (var key of Object.keys(obj)) { 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: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.105 Safari/537.36

Browser/OS: Chrome 84 on Mac OS X 10.15.6

View result in a separate tab

Test name	Executions per second
for-in	1.1 Ops/sec
Object.keys	1.0 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll break down the provided benchmark for you.

**Overview**
The test case measures the performance difference between using traditional `for-in` loop and using the `Object.keys()` method to iterate over an object's properties in JavaScript.

**What is being tested?**

* The `for-in` loop: This is a traditional way of iterating over an object's properties. It uses a loop variable (`key`) that changes on each iteration, allowing access to both the property name and its value.
* The `Object.keys()` method: This is a more modern approach to iterating over an object's properties. It returns an array of strings representing the property names, which can be used in a traditional loop.

**Options being compared**

The benchmark compares two approaches:

1. **Traditional `for-in` loop**: This uses a loop variable (`key`) that changes on each iteration.
2. **Using `Object.keys()` method**: This returns an array of strings representing the property names, which can be used in a traditional loop.

**Pros and Cons**

* **For-in loop**
	+ Pros: Can access both property name and value, easier to use for iterating over arrays or objects with complex logic.
	+ Cons: Can iterate over inherited properties (not recommended), slower performance due to the need to check each property's `in` flag.
* **Object.keys() method**
	+ Pros: Faster performance, more predictable results, does not include inherited properties.
	+ Cons: Requires a traditional loop to access each property name, may not be suitable for arrays or objects with complex logic.

**Library/Language features**

None explicitly mentioned in the benchmark definition.

**Special JS feature/syntax**

The `for...of` loop (not used in this benchmark) and `const` (used in some test cases) are notable JavaScript features. However, they are not relevant to this specific benchmark.

**Other alternatives**

If you want to explore alternative approaches:

* **Using `Array.prototype.forEach()`**: This is a more modern approach to iterating over arrays or objects.
* **Using `for...of` loop**: This is a more concise way of iterating over arrays or objects, but not used in this benchmark.
* **Using a traditional `while` loop with array indices**: This can be a good alternative for arrays, but may not be suitable for objects.

**Benchmark preparation code**

The script prepares an object (`obj`) with 11 properties, all initialized to the value `1`. The script then defines two test cases:

* `for-in`: Uses a traditional `for-in` loop to iterate over the object's properties and logs each property name.
* `Object.keys`: Uses the `Object.keys()` method to get an array of property names, which is then iterated using a traditional `for...loop`.

**Latest benchmark result**

The latest results show that:

* The `for-in` loop performs slightly better than the `Object.keys()` method (approximately 9% faster) on this specific test case.

Related benchmarks:

for-in vs object.keybepb (version: 0)

Comparing performance of: for-in vs Object.keys

Created: 4 years ago by: Guest

Jump to the latest result

for-in

Object.keys

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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