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TESt selector
(version: 0)
test last() function
Comparing performance of:
a vs b
Created:
4 years ago
by:
Guest
Jump to the latest result
HTML Preparation code:
<script src='https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js'></script> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div> <div class="grand"> <div class="parent"> Awesome stuff! </div> <div class="my-class"> <p> I like carrots! </p> </div> </div>
Script Preparation code:
$('*').last().css("background-color", "#cccccc"); //case-1 $('div').last().css("background-color", "#cccccc"); //case-2
Tests:
a
$('*').last().css("background-color", "#cccccc");
b
$('div').last().css("background-color", "#cccccc");
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
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Test case name
Result
a
b
Fastest:
N/A
Slowest:
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Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
I'll break down the provided JSON and explain what's being tested, compared, and other considerations. **Benchmark Definition** The benchmark definition represents a single test case, which is to measure the performance of two different approaches: 1. `$('*').last().css('background-color', '#cccccc');` 2. `$('div').last().css('background-color', '#cccccc');` These two expressions are used to select the last element in the HTML document and set its background color. **Comparison** The two expressions differ in how they select elements: 1. `$('*')` selects all elements on the page, and `.last()` returns the last element among them. 2. `$('div')` selects only elements with the `div` tag name, and `.last()` returns the last one found. **Options Compared** The two options are compared in terms of: 1. **Efficiency**: Which expression is faster? More executions per second? 2. **Selector specificity**: How specific is the selector (e.g., does it target only the intended element)? 3. **Browser support**: Are both expressions supported by different browsers? **Pros and Cons** * `$('*')` last() approach: + Pros: more general, can be used to select any element on the page. + Cons: less efficient due to the unnecessary selection of all elements, potentially slower. * `$('div')` last() approach: + Pros: more specific, targeted at `div` elements only, might be faster for a single element. + Cons: may not work as expected if there are multiple `div` elements with the same class or ID. **Library and Purpose** The jQuery library is used in both expressions. jQuery provides a convenient way to select and manipulate elements on the page, making it easier to write dynamic code. **Special JS Feature/Syntax** There doesn't appear to be any special JavaScript features or syntax being tested here. **Other Alternatives** If you were to rewrite this benchmark without using jQuery, you might consider using more modern JavaScript DOM manipulation APIs, such as `document.body.lastElementChild` or `HTMLElements[0]`. However, these alternatives would likely have similar performance characteristics to the two expressions being compared. Keep in mind that this benchmark is designed to test the performance of a specific code path, and the results might not be representative of real-world usage.
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