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getElementsByClassName()[0] vs querySelectorAll
(version: 0)
Comparing performance of:
By Class Name vs Query Selector
Created:
5 years ago
by:
Guest
Go to the latest result
HTML Preparation code:
<div class="test"></div>
Tests:
By Class Name
document.getElementsByClassName('test')[0];
Query Selector
document.querySelector('.test');
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
By Class Name
Query Selector
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
29 days ago
)
User agent:
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:152.0) Gecko/20100101 Firefox/152.0
Browser/OS:
Firefox 152 on Windows
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=632975" width="100%" height="500px"></iframe>
By Class Name
3.6M/s
Query Selector
3.3M/s
View exact numbers
Test name
Executions per second
✓
By Class Name
3,649,404 Ops/sec
Query Selector
3,344,418 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down what's being tested in the provided JSON. **Benchmark Definition** The website is comparing two approaches to select an HTML element: `document.getElementsByClassName('test')[0]` (By Class Name) and `document.querySelector('.test')` (Query Selector). **Options Compared** There are two options being compared: 1. **By Class Name**: This method uses the `getElementsByClassName()` method, which returns a live HTMLCollection of elements with the specified class name. The `[0]` index is used to access the first element in the collection. 2. **Query Selector**: This method uses the `querySelector()` method, which returns the first element that matches the specified CSS selector. **Pros and Cons** **By Class Name:** Pros: * Wide browser support (not specific to CSS selectors) * Can be more flexible for complex class names Cons: * May return multiple elements if there are multiple elements with the same class name * Can be slower due to the live collection nature of `getElementsByClassName()` Query Selector: Pros: * More precise and efficient, returning only the first matching element * Uses CSS selectors, which can be more concise and expressive Cons: * Requires support for CSS selectors in the browser (not all browsers support this) * Can be slower due to the parsing of CSS selectors **Other Considerations** Both methods have limitations. The `getElementsByClassName()` method may return a live collection, which means that if you modify the DOM after calling `getElementsByClassName()`, it will still return the same elements on subsequent calls. In contrast, `querySelector()` returns a static value and does not pollute the DOM. **Library Usage** The benchmark uses the `document` object, which is part of the DOM (Document Object Model) API. The `document` object provides access to various properties and methods that allow you to interact with an HTML document. **Special JS Features/Syntax** There are no specific JavaScript features or syntax being tested in this benchmark. **Other Alternatives** If you want to measure the performance of different CSS selector algorithms, you could consider adding more test cases, such as: * Using `querySelectorAll()` instead of `querySelector()` * Using different class names or element IDs for comparison * Adding more complex CSS selectors (e.g., `>`, `~`, `[attribute]`) to the benchmark Keep in mind that each additional test case can increase the complexity and scope of the benchmark, which may affect its accuracy.
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querySelector() vs getElementsByClassName()[0]
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