Benchmark: querySelectorAll: id vs tag vs class

HTML Preparation code:

<div>
  <a id="tr_1" class="c-1">
    <span id="tr_2" class="c-2"></span>
  </a>
  <div id="tr_3" class="c-3"></div>
 </div>
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.js'></script>

Tests:

find by id
document.querySelectorAll("#tr_1"); document.querySelectorAll("#tr_2"); document.querySelectorAll("#tr_3");
find by class
document.querySelectorAll(".c-1"); document.querySelectorAll(".c-2"); document.querySelectorAll(".c-3");
find by tag
document.querySelectorAll("a"); document.querySelectorAll("span"); document.querySelectorAll("div");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
find by id
find by class
find by tag

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0

Browser/OS: Firefox 91 on Ubuntu

View result in a separate tab

Test name	Executions per second
find by id	415746.2 Ops/sec
find by class	467583.6 Ops/sec
find by tag	466669.9 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 benchmark and its test cases.

**What is being tested:**

The benchmark tests the performance of three different ways to select elements from an HTML document using JavaScript:

1. **By ID**: `document.getElementById("selector")`
2. **By Class**: `document.querySelectorAll("[class='selector']")` or `document.getElementsByClassName("selector")`
3. **By Tag**: `document.getElementsByTagName("tagName")`

**Options compared:**

The benchmark compares the performance of three different methods for each test case:

1. **Direct selector (e.g., `document.getElementById("#tr_1")`)**: This method uses the `id` attribute to select an element.
2. **Class selector (e.g., `document.querySelectorAll("[class='c-1']")`)**: This method uses the `class` attribute with a value that matches the desired class.
3. **Tag selector (e.g., `document.getElementsByTagName("a")`)**: This method uses the `<tagName>` element.

**Pros and Cons of each approach:**

* **Direct selector**:
	+ Pros: Fast, efficient, and widely supported.
	+ Cons: Can be brittle if IDs change, and may not work as expected with multiple elements having the same ID.
* **Class selector**:
	+ Pros: More flexible than direct selector, works well with multiple elements sharing a class.
	+ Cons: May be slower than direct selector for simple cases, and can be affected by CSS specificity rules.
* **Tag selector**:
	+ Pros: Simple and fast, but may not work as expected if the tag name is not unique.
	+ Cons: Can be less efficient than direct or class selectors, especially with complex HTML.

**Library usage:**

The benchmark uses jQuery (version 3.4.1), which provides a `$.querySelectorAll()` method for selecting elements by class.

**Special JS feature or syntax:**

This benchmark does not use any special JavaScript features or syntax beyond the standard DOM manipulation methods.

**Other alternatives:**

There are other ways to select elements in HTML, such as:

* Using the `querySelector()` method with a CSS selector (e.g., `document.querySelector("#tr_1")`)
* Using the `querySelectorAll()` method with a CSS selector (e.g., `document.querySelectorAll("[class='c-1']")`)

Note that these alternatives may have different performance characteristics compared to the methods tested in this benchmark.

Related benchmarks:

querySelectorAll: id vs tag vs class (version: 0)

test which selector is better for find element

Comparing performance of: find by id vs find by class vs find by tag

Created: 4 years ago by: Guest

Jump to the latest result

find by id

find by class

find by tag

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):