Benchmark: For in vs For object.keys() vs lodash each

HTML Preparation code:


<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Script Preparation code:

var obj = {a:1, b:2, c:3, d:4, f:5, h:6, j:7, i:8, k:9, o:0};

Tests:

For in
var result = {}; for(let i in obj) { result[i] = obj[i]; }
For object keys
var result = {}; var keys = Object.keys(obj); for(let i=0; i<obj.length; ++i) { result[i] = obj[i]; }
Lodash each
var result = {}; _.each(obj, (v, i) => result[i] = v);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
For in
For object keys
Lodash each

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):

LLMs can make mistakes. Check important info.

Let's break down the JavaScript microbenchmark you provided.

**Benchmark Definition**

The benchmark defines three test cases that compare different approaches to iterate over an object:

1. **For in**: uses the `for...in` loop to iterate over the object's properties.
2. **For object keys**: uses the `Object.keys()` method to get an array of the object's property names, and then iterates over it using a traditional `for` loop.
3. **Lodash each**: uses the `_each()` function from the Lodash library to iterate over the object's properties.

**Options Compared**

The benchmark compares three different approaches to achieve the same result:

* `For in`: uses the built-in `for...in` loop, which iterates over both enumerable and non-enumerable properties.
* `For object keys`: uses the `Object.keys()` method to get an array of only enumerable property names, and then iterates over it using a traditional `for` loop.
* `Lodash each`: uses a third-party library (Lodash) to iterate over the object's properties.

**Pros and Cons**

Here's a brief analysis of the pros and cons of each approach:

* **For in**:
	+ Pros: simple, fast, and widely supported. It iterates over both enumerable and non-enumerable properties.
	+ Cons: may include non-enumerable properties in the iteration, which can be undesirable depending on the use case.
* **For object keys**:
	+ Pros: only enumerates over enumerable property names, which can be more predictable than `for...in`.
	+ Cons: requires using an array method (`Object.keys()`), which may incur a small overhead. It also assumes that all properties are enumerable.
* **Lodash each**:
	+ Pros: provides a simple and efficient way to iterate over objects, especially for those already familiar with Lodash's functionality.
	+ Cons: introduces an external dependency (Lodash) and may incur a small performance overhead due to the function call.

**Library: Lodash**

Lodash is a popular JavaScript utility library that provides various functions for working with arrays, objects, and other data structures. The `_each()` function used in this benchmark allows you to iterate over an array or object without having to write explicit loop logic. In this case, it's used to iterate over the `obj` object's properties.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond what's required for the iteration logic.

**Other Alternatives**

If you're interested in exploring alternative approaches, here are a few options:

* **For...of**: This is a more modern iteration approach that can be used with objects. However, it's only supported in ECMAScript 2015+ and may not work in older browsers.
* **Array.prototype.forEach()**: Another way to iterate over an array or object using a callback function.

Overall, the choice of iteration approach depends on your specific use case, performance requirements, and personal preference.

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Windows

View result in a separate tab

Test name	Executions per second
For in	523137.4 Ops/sec
For object keys	994343.1 Ops/sec
Lodash each	833906.3 Ops/sec

Related benchmarks:

For in vs For object.keys() vs lodash each (version: 0)

Comparing performance of: For in vs For object keys vs Lodash each

Created: one year ago by: Registered User

Jump to the latest result

For in

For object keys

Lodash each

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 24 days ago):