Benchmark: getElementById vs querySelector vs getElementsByClassName vs getElementsByName vs querySelectorAll

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;
querySelectorAll
var test = doc.getElementById('testdiv').querySelectorAll('.unique')[0].innerHTML;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
getElementsByTagName
querySelector
getElementsByClassName
getElementsByName
querySelectorAll

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, compared options, pros and cons of each approach, library usage, special JS features or syntax, and other alternatives.

**Benchmarked Issue:**
The benchmark tests the performance of different ways to get just one particular DOM element. Specifically, it compares:

1. `getElementById`
2. `getElementsByTagName`
3. `querySelector`
4. `getElementsByClassName`
5. `getElementsByName` (which is not a standard method and seems to be an error or a custom implementation)
6. `querySelectorAll`

**Methods Compared:**

### 1. `getElementById`

`getElementById` retrieves the element by its id attribute.

Pros:

* Widely supported across browsers
* Fast, as it directly accesses the DOM element by its id

Cons:

* May not work if the element is dynamically generated or loaded after the script execution

### 2. `getElementsByTagName`

`getElementsByTagName` retrieves an array of elements by their tag name.

Pros:

* Can be used to get all elements with a specific tag, which may be useful in certain scenarios

Cons:

* Returns an array of elements, which can lead to slower performance due to DOM lookup
* May not be the best choice when you only need one element

### 3. `querySelector`

`querySelector` retrieves the first element that matches the specified CSS selector.

Pros:

* Fast and efficient, as it uses a optimized CSS selector engine
* Can be used with complex selectors to select multiple elements or attributes

Cons:

* May not work if the element is dynamically generated or loaded after the script execution
* Requires additional setup for attribute selection (e.g., `querySelector('[attribute]')`)

### 4. `getElementsByClassName`

`getElementsByClassName` retrieves an array of elements by their class name.

Pros:

* Fast and efficient, as it uses a optimized DOM lookup
* Can be used with multiple classes in the selector (e.g., `document.querySelector('.class1.class2')`)

Cons:

* May not work if the element is dynamically generated or loaded after the script execution
* Returns an array of elements, which can lead to slower performance due to DOM lookup

### 5. `getElementsByName`

This method seems to be an error or a custom implementation. It's not a standard method and may not work across different browsers.

**Library Usage:**
The benchmark uses the following libraries:

* None (the methods are built-in JavaScript functions)

**Special JS Features/Syntax:**

None mentioned in this specific benchmark

**Other Alternatives:**

For faster and more efficient DOM lookups, you can use other approaches like:

* Using `querySelector` with attribute selectors (`[attribute]`)
* Utilizing the `closest()` method to find elements within a specific scope
* Leveraging modern libraries like jQuery or React for DOM manipulation

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/95.0.4638.69 Safari/537.36 Edg/95.0.1020.44

Browser/OS: Chrome 95 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
getElementById	7039902.0 Ops/sec
getElementsByTagName	3034915.8 Ops/sec
querySelector	3186678.5 Ops/sec
getElementsByClassName	3487994.2 Ops/sec
getElementsByName	3982807.2 Ops/sec
querySelectorAll	1618390.2 Ops/sec

Related benchmarks:

getElementById vs querySelector vs getElementsByClassName vs getElementsByName vs querySelectorAll (version: 0)

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

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

Created: 2 years ago by: Guest

Jump to the latest result

getElementById

getElementsByTagName

querySelector

getElementsByClassName

getElementsByName

querySelectorAll

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 25 days ago):