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Test length assign
(version: 0)
Comparing performance of:
no var vs use var
Created:
3 years ago
by:
Guest
Jump to the latest result
Script Preparation code:
var obj = Array.from({ length: 10000 }).map((value, i) => i).reduce((val, v) => { val[v] = v; return val; }, {})
Tests:
no var
const entries = Object.values(obj); for (let i = 0; i < entries.length; i++) { const v = entries[i]; }
use var
const entries = Object.values(obj); const len = entries.length; for (let i = 0; i < len; i++) { const v = entries[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 var
use var
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 benchmark and its results. **Benchmark Definition** The benchmark measures how fast two different approaches are to iterate over an object in JavaScript: 1. **"Use var"**: This approach uses the `var` keyword to declare variables within the scope of the loop. 2. **"No var"**: This approach does not use the `var` keyword, instead using the `const` keyword for constant variables or relying on the `let` keyword for declared but reassignable variables. **Options Compared** The benchmark compares the performance of these two approaches in terms of: * Speed (measured by "ExecutionsPerSecond") * Use of `var`, `const`, and `let` **Pros and Cons** ### "Use var" Pros: * Can be more efficient in certain cases, as it allows for faster scope resolution * Easier to write and understand for beginners Cons: * Can lead to hoisting issues if not used carefully (e.g., using `var` inside a loop that's not immediately followed by the loop declaration) * May cause more confusion due to its older syntax ### "No var" Pros: * More modern and explicit syntax * Avoids hoisting issues * Generally considered better practice for new code Cons: * Can lead to slightly slower performance in some cases (depending on the specific use case) **Library** None are used in this benchmark. However, if you notice any libraries being used elsewhere in your benchmarking efforts, please let me know and I'd be happy to help. **Special JS Features or Syntax** This benchmark uses: * `let` for declared but reassignable variables (not explicitly mentioned in the benchmark definition, but implied by not using `var`) * `const` for constant variables (used in "No var" approach) * Arrow functions (`=>`) and template literals (`\r\n`) for concise code snippets **Other Considerations** This benchmark seems to be primarily focused on measuring performance differences between these two approaches. However, keep in mind that there might be other factors at play, such as: * The size of the object being iterated over (the `Array.from` approach creates an array with 10,000 elements) * The specifics of the JavaScript engine or browser being used * Potential side effects or memory allocations during execution **Alternatives** If you want to extend this benchmark or explore other variations: * Measure performance differences for other JavaScript features, such as: + Block scope and closure mechanics (e.g., `let` vs. `var` with different scopes) + Object property access patterns + Method calls vs. property accesses on objects * Compare performance across different browsers or JavaScript engines * Consider adding more object sizes or complexity to the iteration process
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