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querySelector vs getElementsByClassName[0] Perf
(version: 0)
Comparing performance of:
QuerySelector vs GetElementsByClassName[0]
Created:
7 years ago
by:
Guest
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HTML Preparation code:
<div class="test"></div>
Tests:
QuerySelector
document.querySelector(".test");
GetElementsByClassName[0]
document.getElementsByClassName("test")[0];
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
QuerySelector
GetElementsByClassName[0]
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided benchmark and explain what's being tested. **Benchmark Overview** The benchmark measures the performance of two approaches to select an HTML element: `document.querySelector` and `document.getElementsByClassName`. The goal is to determine which approach is faster for retrieving a single element by its class name or CSS selector. **Options Compared** Two options are compared: 1. **`document.querySelector`**: This method uses CSS selectors to find the first matching element in the document. 2. **`document.getElementsByClassName`**: This method returns an array of all elements with the specified class name, and we're interested in the first (and only) element. **Pros and Cons** * `document.querySelector`: * Pros: flexible and powerful for selecting multiple elements using CSS selectors, less code required. * Cons: slower than `getElementsByClassName[0]` for single-element retrieval, requires more CPU cycles to parse the selector. * `document.getElementsByClassName`: * Pros: faster for single-element retrieval, uses less CPU cycles since it only returns one element. * Cons: less flexible and powerful compared to `querySelector`, requires explicit indexing to retrieve individual elements. **Library/Functionality** Neither of these functions relies on a library. They are native JavaScript methods built into the DOM API. However, note that the specific behavior might be affected by CSS-specific features like `class` attributes or pseudo-classes like `.test: nth-child(1)` in this benchmark. The alternative for retrieving an element with a given class name would be using a library such as jQuery. It has its own set of methods to retrieve elements, including `$`.
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querySelector vs getElementsByClassName My
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