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document.querySelector vs document.getElementsByClassName
(version: 0)
Comparing performance of:
querySelector vs getElementsByClassName
Created:
3 years ago
by:
Guest
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HTML Preparation code:
<div class="test1"> <p>Hello</p> </div> <div class="test2"> <p>Hello</p> </div> <div class="test3"> <p>Hello</p> </div> <div class="test4"> <p>Hello</p> </div> <div class="test5"> <p>Hello</p> </div> <div class="test6"> <p>Hello</p> </div> <div class="test7"> <p>Hello</p> </div>
Tests:
querySelector
document.querySelector(".test3")
getElementsByClassName
document.getElementsByClassName("test3")
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
Fastest:
N/A
Slowest:
N/A
Latest run results:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the provided JSON benchmark data. **What is being tested?** The main focus of this benchmark is to compare the performance of two DOM manipulation methods in JavaScript: 1. `document.querySelector` 2. `document.getElementsByClassName` These methods are used to retrieve elements from a document based on their class names or CSS selectors. **Options compared** Two options are being compared: * **`document.querySelector`**: This method returns a single element that matches the specified selector, or null if no match is found. * **`document.getElementsByClassName`**: This method returns a live HTMLCollection of all elements with the specified class name. **Pros and Cons:** 1. **`document.querySelector`**: * Pros: + Returns a single element, which can be more efficient when only one match is expected. + Can specify more complex selectors using CSS syntax (e.g., `.test3`). * Cons: + May return null if no match is found, requiring additional checks. 2. **`document.getElementsByClassName`**: * Pros: + Returns a live HTMLCollection, allowing for easier iteration over multiple matches. * Cons: + Returns an array of elements with the specified class name, which can lead to slower performance due to the need to iterate. **Library** In this benchmark, no specific library is being used. The DOM manipulation methods are built-in to JavaScript and do not rely on any external libraries. **Special JS feature or syntax** There are some special features and syntax used in this benchmark: * **CSS selectors**: Both `querySelector` and `getElementsByClassName` use CSS selectors to identify elements. * **JavaScript iteration**: In the test cases, a simple for loop is used to iterate over the returned arrays. **Other alternatives** If you need alternative DOM manipulation methods, some other options include: * **`document.querySelectorAll`**: A similar method to `querySelector`, but returns an HTMLCollection of all matching elements at once. * **`Element.prototype.matches()`**: An older method that uses CSS selectors to match elements. (Note: This method is not supported in older browsers.) * **`CSSOM` APIs**: Other methods like `CSSRuleList`, `CSSStyleRule`, and `CSSStyleSheet` can be used for more advanced DOM manipulation tasks. Overall, the choice between `document.querySelector` and `document.getElementsByClassName` depends on your specific use case and performance requirements. If you need to retrieve a single element or handle complex selectors, `querySelector` might be a better choice. However, if you need to iterate over multiple elements with a specific class name, `getElementsByClassName` could be more suitable.
Related benchmarks:
querySelector vs getElementsByClassName with multiple matching nodes
querySelectorAll vs getElementsByClassName Test
querySelector vs getElementsByClassName on multiple elements
querySelector vs querySelectorAll simple (single element result)
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