Benchmark: Selectors - MeasureThat.net

HTML Preparation code:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min.js">
</script>
<div>
  <ul>
    <li>
      <a href="#" name="name" class="classname">item 1</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 2</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 3</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 4</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 5</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 6</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 7</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 8</a>
    </li>
    <li>
      <a href="#" name="name" class="classname">item 9</a>
    </li>
    <li id="last">
      <a href="#" name="name" class="classname">item 10</a>
    </li>
  </ul>
</div>

Script Preparation code:

var node;

Tests:

querySelector (id)
node = document.querySelector('#last');
getElementById
node = document.getElementById('last');

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector (id)
getElementById

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 16_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.1 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 16 on iOS 16.1

View result in a separate tab

Test name	Executions per second
querySelector (id)	801301.2 Ops/sec
getElementById	1305519.6 Ops/sec

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

LLMs can make mistakes. Check important info.

I'll provide an explanation of the provided benchmark, its options, pros and cons, library usage, special JS features, and alternative approaches.

**Benchmark Definition**
The benchmark compares two ways to select an HTML element using JavaScript: `querySelector` (using an ID selector) and `getElementById`. The script preparation code is a simple `var node;` statement, which initializes the variable without assigning it any value. The HTML preparation code includes a link to jQuery 1.8.1 and a basic HTML structure with an unordered list containing ten list items.

**Individual Test Cases**

### QuerySelector (ID)
```javascript
node = document.querySelector('#last');
```
This test case uses the `querySelector` method to select an element by its ID. In this specific benchmark, it's using the ID `#last`.

*   **Library Usage:** This test case uses the built-in JavaScript DOM API, which doesn't rely on any external libraries.
*   **Special JS Feature:** No special JavaScript features or syntax are used in this test case.

### getElementById
```javascript
node = document.getElementById('last');
```
This test case uses the `getElementById` method to select an element by its ID. In this specific benchmark, it's using the same ID `#last`.

*   **Library Usage:** This test case also uses the built-in JavaScript DOM API and doesn't rely on any external libraries.
*   **Special JS Feature:** No special JavaScript features or syntax are used in this test case.

**Options Compared**
The two test cases compare the performance of:

1.  `querySelector` (using an ID selector)
2.  `getElementById`

These two methods are often compared because they serve similar purposes but have different usage patterns and implications for performance, especially when dealing with large numbers of elements or complex queries.

**Pros and Cons**

### QuerySelector
Pros:

*   **Efficient**: QuerySelector is generally faster than getElementById because it uses a more efficient algorithm that returns the first element matching the specified selector.
*   **Flexible**: Supports CSS selectors, making it easier to write more expressive queries.

Cons:

*   **Browser Support**: QuerySelector is widely supported, but older browsers might not support it. getElementById, on the other hand, has better browser support due to its longer history and wider adoption.

### getElementById
Pros:

*   **Wider Browser Support**: As mentioned earlier, getElementById has better support across different browsers.
*   **Simpler Syntax**: The syntax for getElementById is more straightforward and easier to read.

Cons:

*   **Less Efficient**: As mentioned earlier, getElementById can be slower than QuerySelector due to its less efficient algorithm.

**Considerations**
When choosing between these two methods, consider the following factors:

*   Performance requirements: If you need high performance and support for modern browsers, QuerySelector might be a better choice. However, if you're targeting older browsers or need simpler syntax, getElementById could be more suitable.
*   Complexity of queries: For simple, single-element selections like this benchmark, both methods are effective. However, when dealing with complex queries or large datasets, QuerySelector's flexibility and efficiency make it a better option.

**Alternative Approaches**
If you're looking for alternative approaches to select elements in JavaScript, consider the following:

*   `querySelectorAll`: Returns all elements matching the specified selector. This method is useful when you need to work with multiple elements.
*   CSS selectors: Many modern browsers support CSS selectors natively or through third-party libraries like Sizzle or PureCSS.
*   Regular expressions: While not typically used for HTML element selection, regular expressions can be used in certain situations where a more complex match is needed.

Related benchmarks:

Selectors (version: 0)

Comparing various JS selector speeds

Comparing performance of: querySelector (id) vs getElementById

Created: 7 years ago by: Guest

Jump to the latest result

querySelector (id)

getElementById

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):