Benchmark: querySelector check

HTML Preparation code:

<html>
  <body>
    <div id="test2"></div>
    <div id="test"></div>
    <div class="test-123"></div>
  </body>
</html>

Tests:

querySelector id
document.querySelector("#test");
getElementById
document.getElementById("test");
getElementsByClassName
document.getElementsByClassName("test-123");
querySelector class
document.querySelector(".test-123");

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector id
getElementById
getElementsByClassName
querySelector class

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36

Browser/OS: Chrome 103 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
querySelector id	5333624.0 Ops/sec
getElementById	8068474.0 Ops/sec
getElementsByClassName	9236797.0 Ops/sec
querySelector class	7693742.5 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 provided benchmark and explain what is being tested, the options compared, pros and cons of each approach, and other considerations.

**Benchmark Overview**

The benchmark measures the performance of different DOM manipulation methods in JavaScript: `querySelector`, `getElementById`, `getElementsByClassName`. The test cases are designed to simulate real-world scenarios where these methods are commonly used.

**Options Compared**

1. **`querySelector`**: A method to select elements using a CSS selector.
2. **`getElementById`**: A method to retrieve an element by its ID.
3. **`getElementsByClassName`**: A method to retrieve all elements with a given class name.

**Pros and Cons of Each Approach**

* **`querySelector`**:
	+ Pros: Fast, efficient, and flexible (can be used for multiple selectors). Modern browsers have optimized this method for performance.
	+ Cons: May not work as expected if the DOM is very large or if the selector is complex.
* **`getElementById`**:
	+ Pros: Simple and straightforward. Works well in most cases.
	+ Cons: Less efficient than `querySelector`, especially when dealing with many elements.
* **`getElementsByClassName`**:
	+ Pros: Similar to `querySelector`, but can be used for multiple class names.
	+ Cons: Less efficient than `querySelector`. May return more elements than needed.

**Library and Purpose**

The `document.querySelector` and `document.getElementsByClassName` methods use the W3C DOM API. The purpose of these methods is to provide a way to select and manipulate elements in an HTML document.

**Special JS Feature or Syntax**

None mentioned in this benchmark. No special JavaScript features or syntax are used beyond standard ECMAScript syntax.

**Other Considerations**

* **Browser Support**: The benchmark assumes that the browser being tested supports modern DOM API methods.
* **DOM Size**: The benchmark size is relatively small, which makes it a good test case for performance comparison.
* **Selector Complexity**: The selectors used in this benchmark are simple and straightforward. More complex selectors or larger DOMs would require additional optimization techniques.

**Alternatives**

Other alternatives to these DOM manipulation methods include:

* Using `document.querySelectorAll` (which returns a NodeList) instead of `getElementsByClassName`
* Using `Element.prototype.matches` (for compatibility with older browsers)
* Using third-party libraries like jQuery, which provide their own set of utility functions for DOM manipulation.

Keep in mind that the choice of method depends on the specific use case and requirements.

Related benchmarks:

querySelector check (version: 0)

Comparing performance of: querySelector id vs getElementById vs getElementsByClassName vs querySelector class

Created: 6 years ago by: Guest

Jump to the latest result

querySelector id

getElementById

getElementsByClassName

querySelector class

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):