Benchmark: getElementById vs querySelector vs getElementsByClassName vs getElementsByName

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

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 hours ago)

User agent: Mozilla/5.0 (X11; Linux x86_64; rv:137.0) Gecko/20100101 Firefox/137.0

Browser/OS: Firefox 137 on Linux

View result in a separate tab

Test name	Executions per second
getElementById	7577534.0 Ops/sec
getElementsByTagName	5145454.5 Ops/sec
querySelector	6719074.0 Ops/sec
getElementsByClassName	4566814.5 Ops/sec
getElementsByName	6265701.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 5 months ago):

LLMs can make mistakes. Check important info.

**What is being tested?**

MeasureThat.net is testing the performance of different methods to retrieve a single DOM element in JavaScript. The benchmark compares the execution speed of four methods:

1. `getElementById`
2. `querySelector`
3. `getElementsByClassName`
4. `getElementsByName`

Each method is used to access an element with a specific id, class, or name.

**Options compared:**

The benchmark directly compares the performance of these four methods.

**Pros and Cons of each approach:**

1. **`getElementById`**:
	* Pros: Simple, widely supported, and easy to use.
	* Cons: Can be slow if the element is not found (false positive), which can lead to unnecessary iterations.
2. **`querySelector`**:
	* Pros: More flexible than `getElementById`, allows for more complex selectors.
	* Cons: May be slower due to its more complex parsing mechanism.
3. **`getElementsByClassName`**:
	* Pros: Can retrieve multiple elements with the same class, reducing the number of iterations.
	* Cons: Returns a NodeList (live DOM elements), which can lead to performance issues if not handled correctly.
4. **`getElementsByName`**:
	* Pros: Allows for searching by name attribute, which might be useful in certain scenarios.
	* Cons: Typically slower and less supported than the other methods.

**Libraries and their purposes:**

1. `querySelector`: This is a CSS selector API that allows you to select elements based on various criteria (e.g., id, class, attributes). It's part of the W3C DOM specification.
2. `getElementsByClassName`: This method returns a NodeList containing all elements with the specified class name.

**Special JS features or syntax:**

1. `querySelector` and `getElementsByClassName` use CSS selectors, which are a powerful feature in JavaScript for selecting elements.
2. The `getElementsByName` method uses the `name` attribute to search for elements, which might not be as common as other attributes like `id` or `class`.

**Other alternatives:**

1. **`document.getElementById` with a fallback**: In some cases, using `document.getElementById` and then checking if the result is null can provide better performance than directly using `getElementsByClassName`.
2. **Using libraries like jQuery**: If you need to perform complex DOM manipulations or selections, consider using a library like jQuery, which provides an optimized implementation of CSS selectors.
3. **Using vanilla JavaScript alternatives**: Depending on your specific use case, you might be able to optimize performance by using alternative methods like `document.querySelectorAll` (for all elements matching the selector) or `Array.prototype.filter` and `Element.prototype.matches` (for complex selections).

Related benchmarks:

getElementById vs querySelector vs getElementsByClassName vs getElementsByName (version: 1)

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

Comparing performance of: getElementById vs getElementsByTagName vs querySelector vs getElementsByClassName vs getElementsByName

Created: 8 years ago by: Registered User

Jump to the latest result

getElementById

getElementsByTagName

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 5 months ago):