Benchmark: Object with forIn vs Keys forI

Script Preparation code:

var object = {
	'one':'one',
	'two':'two',
	'three':'three',
	'four':'four',
	'five':'five',
	'six':'six',
	'seven':'seven',
	'eight':'eight',
	'nine':'nine',
	'ten':'ten'
}

Tests:

forIn
for (var key in object) { console.log(object[key], key) }
forI
var keys = Object.keys(object) var length = keys.length var i = -1 while (++i !== length) { var key = keys[i] console.log(object[key], key) }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forIn
forI

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 3 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.77 Safari/537.36 Edg/91.0.864.41

Browser/OS: Chrome 91 on Windows

View result in a separate tab

Test name	Executions per second
forIn	21543.5 Ops/sec
forI	21349.7 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided JSON benchmark definition and test cases.

**Benchmark Definition**

The benchmark measures two approaches for iterating over an object: `forIn` (also known as the "property iteration" method) and `keys for I` (using the `Object.keys()` method to get an array of keys and then iterating using a traditional loop).

**Script Preparation Code**

The script preparation code defines a JavaScript object `object` with 10 properties. This object will be used as the input for the benchmark.

**Html Preparation Code**

There is no HTML preparation code provided, which means that the benchmark only measures the execution time of the JavaScript code.

**Individual Test Cases**

There are two test cases:

1. **forIn**: This test case uses the `for...in` loop to iterate over the properties of the `object`. The loop iterates over each property (key-value pair) and logs both the value and the key to the console.
2. **keys for I**: This test case uses the `Object.keys()` method to get an array of keys from the `object`, and then uses a traditional `while` loop to iterate over the keys. For each key, it logs the corresponding value and key to the console.

**Benchmark Results**

The latest benchmark results show the execution time per second for each test case on a Chrome 91 browser on a Windows Desktop platform.

Now, let's discuss the pros and cons of each approach:

**forIn**:

Pros:

* Simple and intuitive syntax
* Works with all types of objects (not just plain JavaScript objects)
* Can be used to iterate over object properties that have getter or setter methods

Cons:

* Iterates over both own enumerable properties and inherited properties
* May iterate over symbolic properties if the object has them
* Can be slower due to the overhead of iterating over property descriptors

**keys for I**:

Pros:

* More efficient than `forIn` because it only iterates over the object's own enumerable properties
* Provides more control over iteration, as you can choose which keys to iterate over
* Works with objects that have non-enumerable properties (using `Object.getOwnPropertyNames()` or `Object.getOwnPropertySymbols()`)

Cons:

* Requires additional setup to get an array of keys from the object
* Can be slower than `forIn` if the object is very large, as it requires creating an array of keys and then iterating over it

**Library/Tool Considerations**

There doesn't seem to be any specific library or tool used in these benchmark tests. However, the use of `Object.keys()` and `for...in` suggests that JavaScript's built-in object iteration methods are being compared.

**Special JS Features/Syntax**

There doesn't appear to be any special JavaScript features or syntax used in these benchmark tests. Both approaches rely on standard JavaScript syntax and built-in object iteration methods.

**Other Alternatives**

If you wanted to create a similar benchmark, you could also consider using other approaches for iterating over objects, such as:

* Using `for...of` loop with an iterator
* Using `Array.prototype.forEach()` or `Array.prototype.map()`
* Using a third-party library like Lodash

However, these alternatives may not be as relevant to the specific benchmark being tested, which focuses on comparing two standard JavaScript approaches: `forIn` and `keys for I`.

Related benchmarks:

Object with forIn vs Keys forI (version: 0)

Comparing performance of: forIn vs forI

Created: 3 years ago by: Registered User

Jump to the latest result

forIn

forI

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):