Benchmark: getElementById vs querySelector, with ten elements

HTML Preparation code:

<div id="testElement1"></div>
<div id="testElement2"></div>
<div id="testElement3"></div>
<div id="testElement4"></div>
<div id="testElement5"></div>
<div id="testElement6"></div>
<div id="testElement7"></div>
<div id="testElement8"></div>
<div id="testElement9"></div>
<div id="testElement10"></div>

Tests:

getElementById
var el = document.getElementById('testElement1'); var className = el.className;
querySelector
var el = document.querySelector('#testElement1'); 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 (Windows NT 10.0; Win64; x64; rv:122.0) Gecko/20100101 Firefox/122.0

Browser/OS: Firefox 122 on Windows

View result in a separate tab

Test name	Executions per second
getElementById	7635707.5 Ops/sec
querySelector	3896872.2 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 is being tested, compared, and the pros/cons of each approach.

**What is being tested?**

The benchmark tests two ways to retrieve an element by its ID in HTML documents:

1. `document.getElementById('testElement1')`
2. `document.querySelector('#testElement1')`

Both methods are used to get a reference to an HTML element with the specified ID, and then extract the value of the `className` property from that element.

**Options compared:**

The two options being compared are:

1. **`document.getElementById()`**: This method returns a single element that matches the specified ID. It is a more traditional way of accessing elements in HTML documents.
2. **`document.querySelector()`**: This method returns the first element that matches the specified CSS selector, which includes IDs.

**Pros and Cons:**

### `document.getElementById()`

Pros:

* More predictable behavior, as it only returns one element, even if there are multiple elements with the same ID (although this is not recommended in modern web development).
* Often considered more "traditional" or "legacy" way of accessing elements.

Cons:

* Can be slower than `querySelector` for large numbers of elements, since it has to search through all possible matches.
* Does not support CSS selectors like `#id` syntax.

### `document.querySelector()`

Pros:

* More flexible and powerful, as it supports CSS selectors that can match multiple elements with the same ID or other attributes.
* Can be faster for large numbers of elements, since it only returns the first match.

Cons:

* Less predictable behavior, since it can return any element that matches the selector, including multiple elements with the same ID.
* Requires proper syntax and context to use effectively (e.g., `#testElement1` instead of just `testElement1`).

**Library:**

In this benchmark, there is no explicit library mentioned. However, note that if you're using a JavaScript framework or library like jQuery, it may provide its own version of these methods or offer additional functionality.

**Special JS features or syntax:**

None mentioned in the provided code snippets.

**Alternatives:**

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

* Using `document.getElementsByClassName()` (for accessing elements by class name)
* Using `DOMParser` to parse an HTML string and extract elements
* Using a library like jQuery or React to handle DOM manipulation

In summary, the benchmark tests two common ways to access elements in HTML documents using JavaScript: `document.getElementById()` and `document.querySelector()`. While `document.getElementById()` is more traditional and predictable, `document.querySelector()` offers more flexibility and power but requires proper syntax and context.

Related benchmarks:

getElementById vs querySelector, with ten 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):