Benchmark: window.getComputedStyle vs. offsetTop

HTML Preparation code:

<div id="foo"></div>

Tests:

getComputedStyle
var i = 3000; while (i--) { chekele('foo'); } function chekele(element) { return window.getComputedStyle(document.getElementById(element)); }
offsetTop
var i = 3000; while (i--) { chekele('foo'); } function chekele(element) { return document.getElementById(element).offsetTop; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
getComputedStyle
offsetTop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (Linux; Android 12) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/119.0.6045.193 Mobile DuckDuckGo/5 Safari/537.36

Browser/OS: Chrome Mobile 119 on Android

View result in a separate tab

Test name	Executions per second
getComputedStyle	199.6 Ops/sec
offsetTop	32.4 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's dive into the benchmark.

The benchmark is designed to compare two approaches: `window.getComputedStyle` and `offsetTop`. The goal is to determine which method is faster for retrieving the top position of an element on a webpage.

**Options Compared**

1. **`window.getComputedStyle`**: This approach uses the Web API to get the computed style of an element at runtime. It returns an object containing all CSS properties that apply to the element, including its top offset.
2. **`offsetTop`**: This approach directly accesses the `offsetTop` property of an element's bounding rectangle, which represents the vertical distance from the top of the viewport to the top edge of the element.

**Pros and Cons**

* **`window.getComputedStyle`**:
	+ Pros: Can retrieve all CSS properties, including layout values and other metadata.
	+ Cons: May be slower due to the overhead of creating a style object and iterating over its properties.
* **`offsetTop`**:
	+ Pros: Typically faster since it only accesses a single property and doesn't require creating an intermediate object.
	+ Cons: Only retrieves the top offset, not all CSS properties.

**Library Usage**

None of the test cases use any external libraries. However, `document.getElementById` is used to retrieve an element from the DOM, which suggests that the benchmark is focused on the client-side JavaScript engine's performance.

**Special JS Features/Syntax**

The benchmark uses a special syntax in its test cases: the `chekele` function. This appears to be a custom function name, and it's not a standard JavaScript feature or library. It's likely used only for this specific benchmark to illustrate the difference between `window.getComputedStyle` and `offsetTop`.

**Other Alternatives**

If you want to explore alternative approaches, here are some options:

1. **CSSOM (CSS Object Model)**: This is a standardized API that allows you to access CSS properties on elements. It's similar to `window.getComputedStyle`, but might be faster since it's more optimized for performance.
2. **`getBoundingClientRect()`**: This method returns the rectangle that defines the size and position of an element relative to its nearest positioned ancestor. While not identical to `offsetTop`, it provides some similar information and might be a viable alternative.
3. **Native Web APIs (e.g., `getComputedStyle` on native scripts)**: If you're developing a native mobile app or desktop application using JavaScript, you can leverage the native Web API for computing styles. This might provide better performance than client-side JavaScript approaches.

Keep in mind that these alternatives might not be directly comparable to the original benchmark, as they have different use cases and requirements.

Related benchmarks:

window.getComputedStyle vs. offsetTop (version: 0)

Comparing performance of: getComputedStyle vs offsetTop

Created: 2 years ago by: Guest

Jump to the latest result

getComputedStyle

offsetTop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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