Benchmark: getElementById vs querySelector, with two elements

HTML Preparation code:

<div id="testElement"></div>
<div id="secondTestElement"></div>

Tests:

getElementById
var el = document.getElementById('testElement'); var className = el.className;
querySelector
var el = document.querySelector('#testElement'); var className = el.className;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getElementById
querySelector

Fastest: N/A

Slowest: N/A

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/120.0.0.0 Safari/537.36

Browser/OS: Chrome 120 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
getElementById	5186238.5 Ops/sec
querySelector	2651114.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what is tested, compared, and their pros/cons.

**Benchmark Definition**

The benchmark tests two different ways to retrieve an HTML element by its ID: `document.getElementById` and `document.querySelector`. Both methods are used to access an element with the id "testElement" that appears twice in the prepared HTML code.

**Options Compared**

Two options are compared:

1. **`document.getElementById('testElement')`**: This method uses a traditional DOM-based approach to retrieve an element by its ID.
2. **`document.querySelector('#testElement')`**: This method uses CSS selectors to retrieve an element that matches the specified selector.

**Pros and Cons**

**`document.getElementById('testElement')`**

Pros:

* Well-established, widely supported, and easy to use.
* Provides direct access to the DOM node.

Cons:

* Can be slower due to the need to traverse the DOM tree.
* May have limitations when dealing with complex or dynamic elements.

**`document.querySelector('#testElement')`**

Pros:

* More flexible and powerful than `getElementById`, allowing for more complex selectors.
* Can reduce the need for explicit DOM manipulation.

Cons:

* Less widely supported, especially in older browsers.
* May require additional setup or libraries to work correctly.

**Library: CSSOM (CSS Object Model)**

The `document.querySelector` method uses the CSS Object Model (CSSOM), which allows for the selection of elements based on their CSS styles. The CSSOM is a powerful tool that enables developers to write more flexible and efficient code.

**Other Considerations**

When choosing between these two approaches, consider the following:

* If you need to retrieve an element by its ID in a simple or legacy application, `document.getElementById` might be a better choice due to its widespread support.
* For more complex or dynamic applications, `document.querySelector` with CSS selectors can provide more flexibility and power.

**Alternatives**

If you're interested in exploring other alternatives, consider the following:

* **`document.querySelectorAll('#testElement')`**: This method returns an array of elements that match the specified selector. It's similar to `querySelector`, but instead of returning a single element, it returns multiple elements.
* **`Element.prototype.querySelector`**: Some modern browsers and libraries provide this method on the `Element` prototype, allowing for more flexible CSS selector usage.

In summary, the benchmark tests two common ways to retrieve an HTML element by its ID in JavaScript: traditional DOM-based `document.getElementById` and CSS-based `document.querySelector`. While both methods have their pros and cons, `document.querySelector` with CSS selectors offers more flexibility and power, but may require additional setup or libraries for older browsers.

Related benchmarks:

getElementById vs querySelector, with two elements (version: 0)

Comparing performance of: getElementById vs querySelector

Created: 2 years ago by: Guest

Jump to the latest result

getElementById

querySelector

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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