Benchmark: js 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) { if (obj.hasOwnProperty(key)) { console.log(key); } } }
object.keys
for (var i=10000; i > 0; i--) { Object.keys(obj).forEach(key => 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: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 11_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.4992.108 Safari/537.36

Browser/OS: Chrome 102 on Mac OS X 11.1

View result in a separate tab

Test name	Executions per second
for in	1.5 Ops/sec
object.keys	1.5 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested.

**Benchmark Overview**

The benchmark compares two approaches to iterating over an object: using the `for` loop with the `in` keyword (`"for in"`), and using the `Object.keys()` method (`"object.keys"`).

**Options Compared**

The test cases are comparing:

1. **For-in Loop**: Iterates over the keys of an object using a traditional `for` loop, where the variable `i` is not used explicitly.
2. **Object.keys() Method**: Uses the built-in `Object.keys()` method to get an array of the object's property names.

**Pros and Cons**

### For-in Loop

Pros:

* Can be more readable and easier to understand for simple iterations
* Does not require the use of a separate variable (in this case, `i` is used but its purpose is unclear)

Cons:

* Performance: Generally slower than using `Object.keys()` due to the overhead of iterating over the object's own enumerable properties.
* Compatibility: May not work as expected in older browsers or environments.

### Object.keys() Method

Pros:

* Performance: Faster and more efficient, especially for large objects.
* Compatibility: Works consistently across modern browsers and JavaScript engines.

Cons:

* Less readable than the `for-in` loop, requiring a good understanding of how the method works.
* May not be as intuitive for complex iterations or when dealing with non-enumerable properties.

**Other Considerations**

When choosing between these two approaches, consider the trade-off between readability, performance, and compatibility. For simple use cases, the `for-in` loop may be sufficient. However, if performance is critical or you're working with large datasets, using the `Object.keys()` method is likely a better choice.

**Library Usage**

There are no external libraries being used in this benchmark.

**Special JS Features or Syntax**

None mentioned in the provided benchmark definition.

Related benchmarks:

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

Comparing performance of: for in vs object.keys

Created: 7 years ago by: Guest

Jump to the latest result

for in

object.keys

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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