Benchmark: getElementById vs querySelector vs getElementsByClassName vs getElementsByName no double id

HTML Preparation code:

<div id="testdiv">
  <div id="unique" class="unique" name="unique" data-unique="1">test</div>
</div>

Script Preparation code:

var i, imax;
var doc = document;

Tests:

getElementById
var test = doc.getElementById('testdiv').childNodes[0].innerHTML;
querySelector
var test = doc.querySelector('.unique').innerHTML;
getElementsByClassName
var test = doc.getElementsByClassName('unique')[0].innerHTML;
getElementsByName
var test = doc.getElementsByName('unique')[0].innerHTML;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector
getElementsByClassName
getElementsByName

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.108 Safari/537.36

Browser/OS: Chrome 74 on Windows

View result in a separate tab

Test name	Executions per second
getElementById	2639749.8 Ops/sec
querySelector	1146847.8 Ops/sec
getElementsByClassName	1054873.2 Ops/sec
getElementsByName	1029929.2 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's being tested, the pros and cons of each approach, and other considerations.

**Benchmark Purpose**

The benchmark measures the performance of four different ways to retrieve a single DOM element from an HTML document:

1. `getElementById`
2. `querySelector`
3. `getElementsByClassName` (returns an array)
4. `getElementsByName` (not supported in modern browsers, returns an empty array)

**Approaches Compared**

Here's a brief overview of each approach and their pros and cons:

### 1. `getElementById`

* Uses the `id` attribute to identify the element
* Returns a single element if found, or `null` otherwise
* Pros:
	+ Fast and efficient (most browsers use this method internally)
	+ Simple and widely supported
* Cons:
	+ Can be brittle if used with non-unique IDs

### 2. `querySelector`

* Uses CSS selectors to identify the element
* Returns a single element if found, or `null` otherwise
* Pros:
	+ Flexible and powerful (can use complex CSS selectors)
	+ Modern browsers support this method
* Cons:
	+ Can be slower than `getElementById` due to parsing and execution of CSS selectors

### 3. `getElementsByClassName`

* Uses the `class` attribute to identify elements by their class names
* Returns an array of elements with matching class names
* Pros:
	+ Flexible (can use multiple class names in a single selector)
	+ Wide support across browsers
* Cons:
	+ Can return multiple elements, which may not be what's expected
	+ Slower than `getElementById` or `querySelector`

### 4. `getElementsByName` (not supported)

* Uses the `name` attribute to identify elements by their names
* Returns an array of elements with matching names
* Pros:
	+ None (not supported in modern browsers)
* Cons:
	+ Not supported across browsers, making it unreliable

**Library Usage**

The benchmark uses the following libraries:

1. `document`: The DOM (Document Object Model) library is used to interact with HTML documents.
2. No other libraries are mentioned.

**Special JavaScript Features/Syntax**

There are no special features or syntax being tested in this benchmark. However, it's worth noting that some of these methods may rely on specific browser implementations or quirks:

* `querySelector` relies on the CSS Selectors API, which is supported by modern browsers.
* `getElementsByClassName` relies on the W3C standard for class name selection.

**Alternatives**

If you need to measure performance for different DOM element retrieval methods, consider using alternative benchmarks that test specific scenarios or use different measurement techniques. For example:

1. Benchmarking the speed of CSS selector parsing and execution.
2. Comparing the performance of multiple libraries (e.g., jQuery vs vanilla JavaScript).
3. Testing the speed of specific web development frameworks (e.g., React, Angular).

Keep in mind that benchmarking is an essential part of software engineering, and understanding the strengths and weaknesses of different approaches can help you make informed decisions about your codebase.

Related benchmarks:

getElementById vs querySelector vs getElementsByClassName vs getElementsByName no double id (version: 0)

Test performance of different ways of get just one particular DOM element

Comparing performance of: getElementById vs querySelector vs getElementsByClassName vs getElementsByName

Created: 5 years ago by: Guest

Jump to the latest result

getElementById

querySelector

getElementsByClassName

getElementsByName

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):