Benchmark: for-in vs object.keys forEach

Script Preparation code:

var array = [1,2,3,4,5,6,7,8];
var obj = {
  'a': 1,
  'b': 1,
  'c': 1,
  'd': 1,
  'e': 1,
  'f': 1,
  'g': 1,
  'h': 1
};

Tests:

for-in
array.forEach(item => { for (var key in obj) { console.log(key); } });
Object.keys
array.forEach(item => { 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:

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

LLMs can make mistakes. Check important info.

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

**Benchmark Definition**

The benchmark measures the performance of two approaches to iterate over an object in JavaScript:

1. `for-in`: This approach uses the `for` loop with the `in` keyword to iterate over the object's own enumerable properties.
2. `Object.keys()` + `forEach`: This approach uses the `Object.keys()` method to get an array of the object's own enumerable property names, and then iterates over this array using the `forEach` method.

**Options Compared**

The two approaches being compared are:

* `for-in`
* `Object.keys()` + `forEach`

**Pros and Cons of Each Approach**

1. **`for-in`**:
	* Pros:
		+ More traditional and familiar way to iterate over objects.
		+ Can be more efficient for small objects or objects with a limited number of properties.
	* Cons:
		+ Iterates over all own enumerable properties, including inherited ones.
		+ May not work as expected if the object has non-enumerable properties (e.g., getters or setters).
2. **`Object.keys()` + `forEach`**:
	* Pros:
		+ More efficient and modern way to iterate over objects.
		+ Does not iterate over inherited properties.
		+ Can be more concise and easier to read for large objects.
	* Cons:
		+ May require a modern JavaScript engine that supports `Object.keys()`.
		+ Can be less intuitive for developers familiar with traditional object iteration.

**Library Used**

The benchmark uses the `forEach` method, which is a built-in method of the Array prototype in JavaScript. It's not a specific library, but rather a standard part of the JavaScript language.

**Special JS Feature/Syntax**

There is no special JavaScript feature or syntax being tested in this benchmark. The focus is on comparing two different approaches to iterating over an object.

**Other Alternatives**

If you want to test other approaches to iterating over objects, some alternatives include:

* `for...in` with a filter (e.g., `for (var key in obj) if (key !== 'someNonEnumerableProperty') { ... }`)
* Using the `Object.values()` or `Object.entries()` methods instead of `Object.keys()`
* Using a library like Lodash or Ramda for functional programming approaches

Note that these alternatives may not be directly comparable to the original `for-in` and `Object.keys()` + `forEach` approaches, as they may have different performance characteristics or require different setup.

Related benchmarks:

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

Comparing performance of: for-in vs Object.keys

Comparing performance of: for-in vs Object.keys

Created: 5 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

No previous run results

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