Benchmark: querySelectorAll vs. getElementsByTagName

HTML Preparation code:

<table id="data-table">
  <tr>
    <th colspan="6">Results</th>
  </tr>
  <tr>
    <td>No</td>
    <td>Competition</td>
    <td>John</td>
    <td>Adam</td>
    <td>Robert</td>
    <td>Paul</td>
  </tr>
  <tr>
    <td>1</td>
    <td>Swimming</td>
    <td>1:30</td>
    <td>2:05</td>
    <td>1:15</td>
    <td>1:41</td>
  </tr>
  <tr>
    <td>2</td>
    <td>Running</td>
    <td>15:30</td>
    <td>14:10</td>
    <td>15:45</td>
    <td>16:00</td>
  </tr>
  <tr>
    <td>3</td>
    <td>Shooting</td>
    <td>70%</td>
    <td>55%</td>
    <td>90%</td>
    <td>88%</td>
  </tr>
</table>

Script Preparation code:

var dataTable = document.getElementById('data-table');

Tests:

querySelectorAll
dataTable.querySelectorAll("tr")
getElementsByTagName
dataTable.getElementsByTagName('TR')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelectorAll
getElementsByTagName

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):

LLMs can make mistakes. Check important info.

**Overview of the Benchmark**

The provided JSON represents a JavaScript benchmark that compares the performance of two DOM manipulation methods: `querySelectorAll` and `getElementsByTagName`. The benchmark is designed to test how quickly these methods can traverse an HTML table element (`dataTable`) and retrieve all its descendant elements.

**Methods Compared**

The benchmark tests two methods:

1. **`querySelectorAll`**: This method returns a NodeList containing all elements that match the specified CSS selector.
2. **`getElementsByTagName`**: This method returns a collection of elements with the specified tag name.

**Pros and Cons of Each Approach**

### `querySelectorAll`

Pros:

* More expressive and flexible than `getElementsByTagName`, allowing for more complex selectors.
* Can be faster than `getElementsByTagName` because it uses a single operation to retrieve all matching elements, whereas `getElementsByTagName` requires multiple calls to iterate over the table rows.

Cons:

* May have slower performance in older browsers or with very large datasets due to its flexibility and the need to parse CSS selectors.

### `getElementsByTagName`

Pros:

* Faster than `querySelectorAll` for simple cases, as it only needs to find a single element.
* More reliable and robust in older browsers that don't support CSS selectors.

Cons:

* Less expressive and less flexible than `querySelectorAll`, requiring multiple calls to retrieve all elements.
* May be slower for complex selections or large datasets due to the need for iterative searches.

**Library Usage**

The benchmark uses the `document` object, which is a built-in JavaScript library that provides access to HTML documents. The `document.getElementById` method is used to select an element by its ID, in this case, `dataTable`.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntaxes used in this benchmark.

**Other Considerations**

The benchmark assumes that the input HTML structure is a table with rows and columns. If the table structure changes, the benchmark may need to be updated to accommodate the new structure.

**Alternatives**

Other alternatives for comparing these methods could include:

* Using `querySelector` instead of `querySelectorAll`, which would test only the first matching element.
* Using `getElementsByClassName` or `getElementsByTagNameNS` to test other DOM selection methods.
* Creating a more complex HTML structure with multiple tables, rows, and columns to simulate real-world scenarios.

Overall, this benchmark provides a useful comparison of two widely used JavaScript methods for DOM manipulation.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/108.0.0.0 Safari/537.36

Browser/OS: Chrome 108 on Linux

View result in a separate tab

Test name	Executions per second
querySelectorAll	129900.1 Ops/sec
getElementsByTagName	920361.6 Ops/sec

Related benchmarks:

querySelectorAll vs. getElementsByTagName (version: 0)

Comparing performance of: querySelectorAll vs getElementsByTagName

Created: 5 years ago by: Guest

Jump to the latest result

querySelectorAll

getElementsByTagName

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 27 days ago):