Benchmark: getElementById vs querySelector 2

HTML Preparation code:

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

Tests:

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

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: one year ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/136.0.0.0 Safari/537.36

Browser/OS: Chrome 136 on Linux

View result in a separate tab

Test name	Executions per second
getElementById	45952932.0 Ops/sec
querySelector	9370047.0 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 benchmark and explain what's being tested.

**Overview**

The benchmark compares the performance of two methods to retrieve an HTML element: `document.getElementById` (also known as the "old way") and `document.querySelector`. The test checks which method is faster for a specific scenario, where an HTML div with the id "testElement" is created.

**Options Compared**

Two options are being compared:

1. **`document.getElementById`**: This method retrieves an element by its ID using the ` getElementById` function. It's a legacy method that has been around since HTML 3.2 (1997).
2. **`document.querySelector`**: This method retrieves elements that match a specified CSS selector using the `querySelector` function. It was introduced in HTML5 and is more flexible than `getElementById`.

**Pros and Cons**

Here are some pros and cons of each approach:

* `document.getElementById`:
	+ Pros: Simple, widely supported, and easy to use.
	+ Cons: Can be slower for complex selectors or large datasets, as it requires a full DOM traversal.
* `document.querySelector`:
	+ Pros: More powerful and flexible than `getElementById`, allowing for more efficient searching of elements using CSS selectors. It's also generally faster than `getElementById`.
	+ Cons: Can be slower for simple use cases where the selector is not optimized, as it requires parsing and executing a CSS query.

**Library/Features Used**

Neither library or feature is explicitly mentioned in the benchmark definition, but we can infer some characteristics:

* The test uses the `document` object, which is part of the browser's global scope.
* The `querySelector` method is used with a simple CSS selector (`#testElement`), which implies that it requires parsing and executing a CSS query.

**Special JS Features/Syntax**

There are no special JavaScript features or syntax mentioned in this benchmark. It only uses standard JavaScript functions and syntax, such as variable declarations and assignment.

**Alternatives**

Other alternatives to `document.getElementById` and `document.querySelector` include:

* `querySelectorAll`: Similar to `querySelector`, but returns a NodeList with all elements that match the selector.
* `getElementsByClassName` or `getElementByTagName`: These methods retrieve elements based on their class names or tag names, respectively.

In summary, this benchmark compares the performance of two common methods for retrieving HTML elements in JavaScript: `document.getElementById` and `document.querySelector`. The test shows that `querySelector` is generally faster than `getElementById`, but only when optimized with a well-crafted CSS selector.

Related benchmarks:

getElementById vs querySelector 2 (version: 0)

Comparing performance of: getElementById vs querySelector

Created: 5 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):