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array last
(version: 0)
array last
Comparing performance of:
length vs direct
Created:
5 years ago
by:
Guest
Jump to the latest result
Script Preparation code:
var myArray = ["box984", "box985", "box986", "box987", "box988", "box989", "box986", "box987", "box988", "box989", "box986", "box987", "box988", "box989", "box986", "box987", "box988", "box989"]
Tests:
length
myArray[myArray.length-1]
direct
myArray[10]
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
length
direct
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 benchmark definition and test cases. **Benchmark Definition:** The benchmark is focused on measuring the performance of accessing elements at specific indices in an array. The script preparation code defines an array `myArray` containing 24 string elements, with some duplicate values to ensure that the browser has to look up each element by name when using the index-based approach (more on this later). **Options Compared:** Two options are compared: 1. **Index-Based Approach**: This involves accessing an array element using its index (e.g., `myArray[10]`). 2. **Lookup-Based Approach**: In JavaScript, arrays store their elements in contiguous blocks of memory, and when you access an element by name (using bracket notation), the browser has to perform a lookup to find the correct element in the underlying array. **Pros and Cons:** * Index-Based Approach: + Pros: Faster execution times since the browser can directly access the memory location associated with the index. + Cons: May lead to incorrect results if the JavaScript engine performs optimizations that skip indexing, such as caching or using specialized instructions for array lookups. * Lookup-Based Approach (using bracket notation): + Pros: More accurate results since it takes into account any potential optimizations or caching by the JavaScript engine. + Cons: Slower execution times due to the additional overhead of searching for the correct element in the array. **Library and Purpose:** The `myArray` definition uses a built-in JavaScript feature called **array literals**, which are used to create arrays. The array literal syntax is a concise way to define an array with multiple elements, like this: `[element1, element2, ..., elementN]`. This syntax does not require the use of a separate library. **Special JS Feature or Syntax:** None mentioned in the provided code snippet. **Other Alternatives:** * **Array.prototype.indexOf()**: This method returns the index of the first occurrence of an element within the array. It can be used as an alternative to bracket notation, but it may not provide the same performance benefits. * **Typed arrays**: These are optimized arrays for specific data types (e.g., integers or floats) that can improve performance in certain scenarios. **Benchmark Preparation Code:** The script preparation code creates a large array `myArray` with duplicate values. This is done to ensure that the browser has to perform a lookup to find the correct element when using index-based notation, which is necessary for comparing the two approaches. **Individual Test Cases:** * **Test Case 1:** `"myArray[10]"` - Accesses the 11th element of `myArray` directly using its index. * **Test Case 2:** `"myArray.length-1"` - Returns the last element of `myArray` by subtracting 1 from its length, which is an example of lookup-based notation. The benchmark compares the performance of these two approaches on different browsers and devices to provide insights into their relative performance characteristics.
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