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Check if an element contains a class name using a regular expression (v2)
(version: 0)
Comparing performance of:
loop vs className
Created:
3 years ago
by:
Guest
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HTML Preparation code:
<div class='hello_world one two three four five six seven eight nine testClass' id='demoBlock'></div>
Script Preparation code:
var el = document.getElementById('demoBlock');
Tests:
loop
for (var i=0, l=el.classList.length; i<l; ++i) { if(/hello_[^\s]+/.test(el.classList[i])) { console.log('found') break; } }
className
if (/hello_[^\s]+/.test(el.className)) { console.log('found') }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
loop
className
Fastest:
N/A
Slowest:
N/A
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
I'll break down the provided benchmark definition and test cases to explain what's being tested, compared, and their pros and cons. **Benchmark Definition:** The benchmark is designed to measure the performance of two approaches for checking if an HTML element contains a class name using regular expressions. The two approaches are: 1. **Looping through the `classList` array**: This approach iterates through each class in the `classList` array and uses a regular expression to check if it matches the target string (`hello_[^\\s]+`). If a match is found, the loop breaks. 2. **Using the `className` property with a regular expression**: This approach directly checks the `className` property of the element using a regular expression. **Test Preparation Code:** The script preparation code creates a variable `el` that references an HTML element with the ID "demoBlock". The HTML preparation code defines a simple HTML structure with multiple class names, including "hello_world" and "testClass". **Library and Special Features:** * **`classList` property**: This is a DOM API property that returns an iterable list of classes applied to an HTML element. * **Regular expressions (`/regex/)`**: JavaScript's built-in regular expression engine is used to perform pattern matching. **Options Compared:** The benchmark compares the performance of two approaches: 1. **Looping through `classList` array**: This approach has a time complexity of O(n), where n is the number of classes in the list. 2. **Using `className` property with regular expression**: This approach has a constant time complexity (O(1)) since it only checks the `className` property once. **Pros and Cons:** * **Looping through `classList` array**: + Pros: Can handle multiple class names with different patterns. + Cons: Iterates over all classes, which can be slower for large lists. * **Using `className` property with regular expression**: + Pros: Faster since it only checks the `className` property once. + Cons: May not work correctly if the `className` property contains multiple class names separated by spaces. **Other Considerations:** * The benchmark does not account for cases where the element has multiple classes, and some of them may be separated by spaces (e.g., "hello world"). * The regular expression used in both approaches (`/hello_[^\\s]+/) is designed to match any string starting with "hello_" followed by one or more non-space characters. **Alternatives:** Other alternatives for checking if an element contains a class name could include: * Using the `contains` method of the `CSSClassList` interface (not supported in older browsers) * Using a library like jQuery's `.hasClass()` method * Using a more advanced regular expression or a dedicated regex engine Keep in mind that these alternatives may have different performance characteristics and might not be suitable for all use cases.
Related benchmarks:
classList.contains vs. loop vs regex
Check if an element contains a class name using a regular expression
Check if an element contains a class name using a regular expression (v3)
classList.contains vs. Set vs regex
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