Benchmark: optimizing DOM selectors

HTML Preparation code:

<div id="test"></div>
<div class="test"></div>
<div aria-label="test"></div>

Tests:

getElementById
document.getElementById('test');
querySelector
document.querySelector('#test');
if-else id
var query = '#test'; if (query.startsWith('#')) document.getElementById(query.substring(1)); else document.querySelector(query);
if-else querySelector
var query = '[aria-label]'; if (query.startsWith('#')) document.getElementById(query.substring(1)); else if (query.startsWith('.')) document.getElementsByClassName(query.substring(1)); else document.querySelector(query);

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector
if-else id
if-else querySelector

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; rv:85.0) Gecko/20100101 Firefox/85.0

Browser/OS: Firefox 85 on Windows

View result in a separate tab

Test name	Executions per second
getElementById	5378841.5 Ops/sec
querySelector	2898319.5 Ops/sec
if-else id	3370841.8 Ops/sec
if-else querySelector	948958.6 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 explain what is being tested.

**Overview**

The benchmark measures the performance of different DOM selector methods in JavaScript, specifically when dealing with elements that have both an ID and other attributes (such as `aria-label`).

**Test Cases**

There are four test cases:

1. `getElementById`: Tests the `document.getElementById()` method.
2. `querySelector`: Tests the `document.querySelector()` method.
3. `if-else id`: Tests a custom implementation that uses an if-else statement to check for both IDs and other attributes.
4. `if-else querySelector`: Similar to the previous one, but tests using the `querySelector` method.

**Library Usage**

There is no explicit library usage in these test cases. However, it's worth noting that `document.getElementById()` and `document.querySelector()` are part of the DOM API, which is a standard JavaScript library.

**Special JS Feature/Syntax**

None of the test cases explicitly use any special JavaScript features or syntax. They focus on the performance comparison of different DOM selector methods.

**Options Compared**

The benchmark compares four options:

1. **`getElementById`**: Uses the `document.getElementById()` method, which returns the first element with the specified ID.
2. **`querySelector`**: Uses the `document.querySelector()` method, which returns the first element that matches the specified CSS selector.
3. **`if-else id`**: A custom implementation that checks for both IDs and other attributes using an if-else statement.
4. **`if-else querySelector`**: Similar to the previous one, but uses the `querySelector` method.

**Pros and Cons of Each Approach**

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

1. **`getElementById`**:
	* Pros: Simple, efficient, and widely supported.
	* Cons: May return incorrect results if multiple elements have the same ID.
2. **`querySelector`**:
	* Pros: Flexible, powerful, and can match more complex selectors.
	* Cons: May be slower than `getElementById` for simple cases.
3. **`if-else id`**:
	* Pros: Customizable, allows for efficient handling of multiple IDs.
	* Cons: More complex, may have performance overhead due to the if-else statement.
4. **`if-else querySelector`**:
	* Pros: Similar to `querySelector`, but uses an if-else statement for efficiency.
	* Cons: May be slower than the simple `querySelector` approach.

**Other Considerations**

When choosing a DOM selector method, consider factors such as:

* Complexity of the selector: Simple selectors like IDs are often faster, while more complex selectors may require more resources.
* Frequency of use: If you frequently need to select elements with specific IDs or attributes, an efficient implementation may be crucial.
* Browser support: Different browsers may have varying levels of support for different DOM APIs.

**Alternatives**

Other alternatives to these approaches include:

* Using `document.querySelectorAll()` instead of `querySelectorAll()`, which returns a NodeList instead of a single element.
* Implementing custom logic using regular expressions or other parsing methods.
* Utilizing modern libraries like jQuery, which provides an efficient and feature-rich DOM selector API.

Keep in mind that the best approach will depend on the specific use case and performance requirements.

Related benchmarks:

optimizing DOM selectors (version: 0)

optimizing DOM selectors

Comparing performance of: getElementById vs querySelector vs if-else id vs if-else querySelector

Created: 3 years ago by: Guest

Jump to the latest result

getElementById

querySelector

if-else id

if-else querySelector

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):