Benchmark: for-in vs object.keys

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--) { Object.keys(obj).forEach(key => console.log(key)); }

Historical Performance Data aggregated from 293 community runs

Desktop Results:

Chrome 224 runs

for-in

6/s

Object.keys

5/s

Fastest: for-in (1.2x faster)

View exact numbers

✓ for-in: 6 ops/sec
• Object.keys: 5 ops/sec

Firefox 45 runs

for-in

2/s

Object.keys

2/s

View exact numbers

✓ for-in: 2 ops/sec
• Object.keys: 2 ops/sec

Safari 5 runs

for-in

24/s

Object.keys

20/s

Fastest: for-in (1.2x faster)

View exact numbers

✓ for-in: 24 ops/sec
• Object.keys: 20 ops/sec

Mobile Results:

Chrome 12 runs

for-in

2/s

Object.keys

2/s

Fastest: for-in (1.2x faster)

View exact numbers

✓ for-in: 2 ops/sec
• Object.keys: 2 ops/sec

Safari 7 runs

for-in

26/s

Object.keys

20/s

Fastest: for-in (1.3x faster)

View exact numbers

✓ for-in: 26 ops/sec
• Object.keys: 20 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
for-in
Object.keys

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36

Browser/OS: Chrome 145 on Mac OS X 10.15.7

View result in a separate tab

for-in

7/s

Object.keys

6/s

View exact numbers

Test name	Executions per second
✓ for-in	7 Ops/sec
Object.keys	6 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

**Benchmark Definition**

The benchmark definition is provided in JSON format, which represents two test cases: `for-in` and `Object.keys`. The script preparation code is the same for both test cases, which defines an object `obj` with 7 properties. This object will be used as the input for both tests.

**Options Compared**

The two test cases compare the performance of two approaches to iterate over the properties of the object:

1. **For-in loop**: The first test case uses a traditional `for-in` loop, which iterates over the object's properties using the `in` keyword.
2. **Object.keys() method**: The second test case uses the `Object.keys()` method, which returns an array of the object's property names.

**Pros and Cons**

* **For-in loop**:
	+ Pros: Can be more flexible when working with objects that have custom properties or methods.
	+ Cons: Can be slower due to the overhead of iterating over the object's properties using `in`.
* **Object.keys() method**:
	+ Pros: Fast and efficient, as it uses an internal optimized algorithm to retrieve property names.
	+ Cons: May not work correctly with objects that have custom properties or methods.

In general, `Object.keys()` is a faster approach, but it may not be suitable for all use cases. The choice between the two ultimately depends on the specific requirements of your application.

**Library Used**

There is no explicit library mentioned in the benchmark definition. However, both test cases rely on JavaScript's built-in object and array methods (`Object.keys()`).

**Special JS Feature/Syntax**

Neither test case uses any special JavaScript features or syntax beyond what is required to demonstrate the comparison between the two approaches.

**Other Alternatives**

If you wanted to add more alternatives to this benchmark, some options could include:

1. Using `for...of` loop instead of `for-in` loop.
2. Using `Array.prototype.forEach()` method with an array of property names instead of `Object.keys()`.
3. Using a third-party library like Lodash or Underscore.js for iterating over object properties.

By adding more alternatives, you could provide a more comprehensive comparison and give users more options to explore.

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

Comparing performance of: `for-in vs Object.keys`

Created: 8 years ago by: Guest

Go to the latest result

for-in

Object.keys

Historical Performance Data aggregated from 293 community runs

Desktop Results:

Chrome 224 runs

Firefox 45 runs

Safari 5 runs

Mobile Results:

Chrome 12 runs

Safari 7 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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

Comparing performance of: for-in vs Object.keys

Created: 8 years ago by: Guest

Go to the latest result

for-in

Object.keys

Historical Performance Data aggregated from 293 community runs

Desktop Results:

Chrome 224 runs

Firefox 45 runs

Safari 5 runs

Mobile Results:

Chrome 12 runs

Safari 7 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: `for-in vs Object.keys`