Benchmark: for-of campare2 - MeasureThat.net

Script Preparation code:

for (let i=0 ; i>100;i++){
let img = document.createElement('img');
}

Tests:

var-inside
for (let List of document.getElementsByTagName("img")){ List.classList.add("imgList"); }
var-outside
let ImgList = document.getElementsByTagName("img"); for (let List of ImgList){ List.classList.add("imgList"); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
var-inside
var-outside

Fastest: N/A

Slowest: N/A

Latest run results:

No previous 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 benchmark and explain what is being tested.

**What is being tested?**

The benchmark measures the performance difference between two approaches to iterate over an array of `img` elements in the HTML document:

1. **Using a for-of loop with `document.getElementsByTagName("img")`:** This approach uses the `getElementsByTagName` method to retrieve all `img` elements as an array, and then iterates over it using a for-of loop.
2. **Using a variable declaration (`var`) with `document.getElementsByTagName("img")`:** This approach also retrieves all `img` elements as an array, but declares a variable `ImgList` outside the loop to store the reference to the array.

**Options compared**

The two approaches are being compared for their performance differences in executing the loop. The benchmark aims to determine which approach is faster and more efficient.

**Pros and Cons of each approach:**

1. **For-of loop with `document.getElementsByTagName("img")`**
	* Pros:
		+ Faster iteration over the array, as it avoids the overhead of declaring a variable.
		+ Can be more readable for some developers who are familiar with the syntax.
	* Cons:
		+ May not work correctly if the `getElementsByTagName` method returns an empty array or an array with only one element.
2. **Using a variable declaration (`var`) with `document.getElementsByTagName("img")`
	* Pros:
		+ Works even when the `getElementsByTagName` method returns an empty array or an array with only one element, as the variable can be reassigned.
	* Cons:
		+ Slower iteration over the array due to the overhead of declaring and reassigning a variable.

**Library usage**

In this benchmark, no specific libraries are used beyond the standard JavaScript APIs for interacting with the DOM (Document Object Model).

**Special JS feature or syntax**

The benchmark uses the `for-of` loop, which is a relatively recent addition to the JavaScript language (introduced in ECMAScript 2015). This loop allows iterating over arrays and other iterable objects without needing an explicit index variable.

**Other alternatives**

There are alternative ways to iterate over arrays in JavaScript, such as using traditional for loops with `index` variables or even array methods like `forEach()`:

* **Traditional for loop:** `for (let i = 0; i < img.length; i++) { ... }`
* **Array method (`forEach()`):** `img.forEach((img) => { ... });`

However, these alternatives are not being tested in this benchmark.

I hope this explanation helps!

Related benchmarks:

for-of campare2 (version: 1)

Comparing performance of: var-inside vs var-outside

Created: 4 years ago by: Registered User

Jump to the latest result

var-inside

var-outside

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):