Benchmark: querySelectorAll foreach vs getElementsByClassName [].forEach.call()

HTML Preparation code:

<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>
<div class="test"></div>

Tests:

querySelectorAll foreach
var test = document.querySelectorAll(".test"); test.forEach(el => { var t = el; });
getElementsByClassName [].forEach.call()
var test = document.getElementsByClassName("test"); [].forEach.call(test, el => { var t = el; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll foreach
getElementsByClassName [].forEach.call()

Fastest: N/A

Slowest: N/A

Latest run results:

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

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

The benchmark compares two approaches to iterate over an HTML collection of elements with the class `test`. The two approaches are:

1. `querySelectorAll` followed by `forEach`
2. `getElementsByClassName` followed by `.forEach.call()`

**Option 1: `querySelectorAll` followed by `forEach`**

In this approach, `querySelectorAll` is used to select all elements with the class `test`. The resulting NodeList (a collection of nodes without a length property) is then iterated over using `forEach`. Inside the callback function, each element is assigned to a variable `t`.

**Pros:**

* Efficient way to iterate over an HTML collection
* Does not require additional DOM manipulation or library calls

**Cons:**

* May have performance overhead due to the need to create a NodeList and then iterate over it
* May not be as efficient as native JavaScript methods for certain use cases

**Option 2: `getElementsByClassName` followed by `.forEach.call()`**

In this approach, `getElementsByClassName` is used to select all elements with the class `test`. The resulting HTMLCollection (a collection of nodes with a length property) is then iterated over using `.forEach.call()`, which converts the HTMLCollection to an array-like object that can be iterated over.

**Pros:**

* May have performance overhead due to the need to convert an HTMLCollection to an array-like object
* Does not require additional DOM manipulation or library calls

**Cons:**

* Requires a call to `.forEach.call()` to iterate over the collection, which adds complexity
* May not be as efficient as native JavaScript methods for certain use cases

In the provided benchmark result, `getElementsByClassName` followed by `.forEach.call()` appears to outperform `querySelectorAll` followed by `forEach`. However, it's essential to note that this may vary depending on the specific use case and browser.

The benchmark uses the Chrome 81 browser and a Windows Desktop device. The test is executed 231033.71875 times per second for `getElementsByClassName` and 213875.5625 times per second for `querySelectorAll` followed by `forEach`.

It's worth noting that this benchmark does not consider other factors that may affect performance, such as:

* Browser version and patch level
* System resources (CPU, RAM, etc.)
* Network conditions
* HTML document complexity

Other alternatives to these approaches include:

* Using a library like jQuery or React that provides optimized methods for iterating over DOM collections
* Using a native JavaScript method like `Array.prototype.forEach()` or `Array.from()`
* Using a specialized library or framework that optimizes performance for specific use cases (e.g., Canvas, WebGL)

In summary, the benchmark compares two approaches to iterate over an HTML collection with class `test`. While there are pros and cons to each approach, the results suggest that `getElementsByClassName` followed by `.forEach.call()` may be more efficient in this particular scenario. However, it's essential to consider other factors that may affect performance when choosing a method for your specific use case.

Related benchmarks:

querySelectorAll foreach vs getElementsByClassName [].forEach.call() (version: 0)

Comparing performance of: querySelectorAll foreach vs getElementsByClassName [].forEach.call()

Created: 5 years ago by: Guest

Jump to the latest result

querySelectorAll foreach

getElementsByClassName [].forEach.call()

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):