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for-test1
(version: 0)
Comparing performance of:
no cache length vs with cache length
Created:
7 years ago
by:
Guest
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Tests:
no cache length
const arr = new Array(10000) for (let i = 0; i < arr.length; i++){ console.log(i); }
with cache length
const arr = new Array(10000) for (let i = 0, l = arr.length; i < l; i++){ console.log(i); }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
no cache length
with cache length
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, compared options, their pros and cons, and other considerations. **Benchmark Overview** The benchmark compares two versions of a simple JavaScript loop that logs numbers from 0 to 9,999 in an array. The difference between the two loops lies in how they calculate the `length` property of the array. **Script Preparation Code** The script preparation code is empty, which means that MeasureThat.net assumes that the provided benchmark definition is self-contained and doesn't require any additional setup or initialization. **Benchmark Definition** The benchmark definition consists of two test cases: 1. **"no cache length"`**: This test case uses the original loop syntax: `for (let i = 0; i < arr.length; i++)`. 2. **"with cache length"`**: This test case uses a modified loop syntax with a cached variable for the array length: `for (let i = 0, l = arr.length; i < l; i++)`. **Comparison of Options** The two options being compared are: 1. **Using the original loop syntax (`for (let i = 0; i < arr.length; i++)`):** * Pros: + More concise and readable code. * Cons: + May be slower due to the need to calculate `arr.length` on each iteration. 2. **Using a cached variable for the array length (`for (let i = 0, l = arr.length; i < l; i++)`):** * Pros: + Can be faster because it avoids calculating `arr.length` on each iteration. * Cons: + May lead to slightly longer code and more complex loop logic. **Library Usage** None of the benchmark definitions use any external libraries. **Special JavaScript Feature or Syntax** The test cases demonstrate a subtle aspect of JavaScript's caching mechanism for array length properties. When using `for...of` loops, JavaScript caches the result of accessing an array property on the first iteration. In this case, the cached variable `l` is used to avoid recalculating `arr.length` on each iteration. **Other Considerations** MeasureThat.net likely aims to provide a fair comparison between these two loop optimizations by executing both test cases under identical conditions (e.g., same browser, hardware, and environment). The benchmark results can help developers understand the performance implications of using cached variables for array lengths. **Alternatives** If MeasureThat.net were to compare other loop optimization techniques or JavaScript features, alternatives might include: * Loop unrolling vs. iteration counting * Using `forEach()` with callbacks vs. traditional loops * Comparing performance with and without tree shaking (optimization step that removes unused code) * Evaluating the impact of const/catch block optimization on performance
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