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Local scope vs outer scope variables
(version: 0)
Benchmark.js
Cache variable in the function scope
Comparing performance of:
Cache in the inner scope vs Do not cache at all
Created:
10 years ago
by:
Guest
Go to the latest result
Script Preparation code:
var testVar = 10;
Tests:
Cache in the inner scope
function doTest1(){ var sum = 0; for (var i = 0; i < testVar; i++){ sum = sum + i; } } doTest1();
Do not cache at all
function doTest2(){ var sum = 0; var testVarLocal = testVar; for (var i = 0; i < testVarLocal; i++){ sum = sum + i; } } doTest2();
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
Cache in the inner scope
Do not cache at all
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
6 months ago
)
User agent:
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36
Browser/OS:
Chrome 142 on Linux
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=625730" width="100%" height="500px"></iframe>
Do not cache at all
58.4M/s
Cache in the inner scope
31.9M/s
View exact numbers
Test name
Executions per second
✓
Do not cache at all
58,415,420 Ops/sec
Cache in the inner scope
31,898,638 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's break down the benchmark and its test cases. **Benchmark Purpose** The provided benchmark is designed to compare two approaches to caching variables in JavaScript: 1. **Caching in the outer scope**: The variable `testVar` is defined outside the function `doTest1`. This approach caches the value of `testVar` in the outer scope, making it accessible within the function. 2. **Not caching at all**: In this case, a local variable `sum` is used inside the function `doTest2`, and its value is not cached. Instead, a new variable is created on each iteration. **Options Compared** The benchmark compares the performance of these two approaches: * **Caching in the inner scope** (test case 1): The variable `testVar` is accessed directly within the function. * **Not caching at all** (test case 2): A local variable `sum` is used, and its value is not cached. **Pros and Cons** **Caching in the outer scope:** Pros: * Can be more efficient if the variable's value doesn't change frequently. * Can reduce the number of assignments within the function. Cons: * May lead to variable pollution (hiding side effects) if used excessively. * May cause issues with function scoping and hoisting. **Not caching at all:** Pros: * Ensures that variables are not shared between functions or scopes. * Reduces the risk of variable pollution. * Can be beneficial when working with complex, stateful codebases. Cons: * May lead to increased overhead due to repeated calculations or assignments. * Can result in slower performance for computationally intensive tasks. **Other Considerations** * The benchmark does not account for the use of closures or function hoisting, which can affect variable caching behavior. * The `testVar` value is hardcoded to 10; consider using a more dynamic approach to test the caching behavior under different conditions. **Library and Special JS Features** There are no libraries mentioned in the provided benchmark. However, it's worth noting that some JavaScript engines (e.g., V8) optimize function calls based on the presence of closures or variables captured by closures. This optimization is not directly related to variable caching but can impact performance in certain scenarios. **Alternatives** Other alternatives for testing caching behavior in JavaScript benchmarks include: * Using a library like Benchmark.js, which provides a more comprehensive set of benchmarking tools and features. * Incorporating additional test cases to cover other aspects of caching behavior, such as: + Caching in the global scope + Using WeakMaps or WeakSets for caching + Testing caching performance under different memory constraints Keep in mind that these alternatives would require modifications to the existing benchmark code.
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