Benchmark: querySelector(tag) vs querySelector(#ID)

HTML Preparation code:

<html>

<head>
    <title>Title</title>
    <script></script>
</head>

<body>
    <nav id="menu"></nav>
    <header id="h"></header>
    <main id="content">
      <article></article>
  	</main>
    <footer></footer>
</body>

</html>

Tests:

querySelector by TAG
document.querySelectorAll('HEADER')
querySelector by ID
document.querySelectorAll('#h')

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
querySelector by TAG
querySelector by ID

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's dive into the world of MeasureThat.net and analyze the provided benchmark.

**What is being tested?**

MeasureThat.net is testing two different approaches to query an HTML element using `document.querySelectorAll()`:

1. **Querying by tag name**: This involves passing a string representing the tag name (in this case, "HEADER") to `document.querySelectorAll()`. The function returns a NodeList containing all elements with the specified tag name.
2. **Querying by ID**: This involves passing an ID (in this case, "#h") as a single argument to `document.querySelector()`, which then returns the first element with that ID.

**Options being compared**

The two options being compared are:

* `document.querySelectorAll('HEADER')`
* `document.querySelector('#h')`

These options differ in how they select elements from the DOM. `querySelectorAll()` is used for selecting multiple elements based on a tag name, while `querySelector()` is used for selecting a single element based on an ID.

**Pros and Cons of each approach**

**Querying by Tag Name (`document.querySelectorAll('HEADER')`)**

Pros:

* Can be useful when you need to select multiple elements with the same tag name.
* Allows for more flexibility in your CSS selectors.

Cons:

* Returns all matching elements, which can lead to performance issues if there are many matching elements.
* May not be as efficient as querying by ID since it requires traversing the DOM tree to find all matching elements.

**Querying by ID (`document.querySelector('#h')`)**

Pros:

* Faster than querying by tag name since it allows for a more direct lookup in the DOM.
* Returns only the first matching element, which can reduce memory usage and improve performance.

Cons:

* Limited to selecting only one element based on an ID.
* May not be as flexible as querying by tag name.

**Library/Libraries**

In this benchmark, there is no specific library being used. However, `document.querySelectorAll()` and `document.querySelector()` are built-in DOM methods in JavaScript.

**Special JS feature/Syntax**

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

**Other Alternatives**

If you were to implement a similar benchmark, you might consider using other approaches, such as:

* Using `querySelectorAll()` with the `grep` method to filter results
* Using `querySelectorAll()` with a regular expression to match elements
* Using a library like jQuery that provides its own set of DOM selection methods (although MeasureThat.net seems to focus on native JavaScript implementation)

In conclusion, this benchmark is designed to test the performance differences between two common approaches to selecting elements from an HTML document using `document.querySelectorAll()` and `document.querySelector()`.

Latest run results:

Run details: (Test run date: 4 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/84.0.4147.89 Safari/537.36

Browser/OS: Chrome 84 on Mac OS X 10.15.5

View result in a separate tab

Test name	Executions per second
querySelector by TAG	1532669.9 Ops/sec
querySelector by ID	1018262.8 Ops/sec

Related benchmarks:

querySelector(tag) vs querySelector(#ID) (version: 2)

test querySelector by tag against ID when only one element of that tag name exists

Comparing performance of: querySelector by TAG vs querySelector by ID

Created: 4 years ago by: Registered User

Jump to the latest result

querySelector by TAG

querySelector by ID

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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