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Iterator vs Index for loop (cached array length fixed)
(version: 1)
Comparing performance of:
Iterator for loop vs Index for loop
Created:
3 years ago
by:
Registered User
Go to the latest result
Script Preparation code:
var arr = []; for(let i = 0; i < 10000; i++) { arr.push(Math.random()); } var arrLength = arr.length;
Tests:
Iterator for loop
let sum = 0; for(const num of arr) { sum += num; }
Index for loop
let sum = 0; for(let i = 0; i < arrLength; i++) { sum += arr[i]; }
Rendered benchmark preparation results:
Suite status:
<idle, ready to run>
Run tests (2)
Previous results
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Test case name
Result
Iterator for loop
Index for loop
Fastest:
N/A
Slowest:
N/A
Latest run results:
Run details:
(Test run date:
one year ago
)
User agent:
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/133.0.0.0 Safari/537.36 Edg/133.0.0.0
Browser/OS:
Chrome 133 on Windows
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Embed Benchmark Result
<iframe src="https://measurethat.net/Embed?id=591036" width="100%" height="500px"></iframe>
Index for loop
22K/s
Iterator for loop
19K/s
View exact numbers
Test name
Executions per second
✓
Index for loop
22,204 Ops/sec
Iterator for loop
19,374 Ops/sec
Autogenerated LLM Summary
(model
llama3.2:3b
, generated one year ago):
Let's dive into the provided benchmark and explain what is being tested. The test compares two approaches to iterate over an array: using an iterator (forEach) versus using index-based indexing ( traditional for loops). The array length is fixed at 10,000 elements, which is already cached before running the benchmarks. **Pros and Cons of each approach:** 1. **Iterator (forEach) Approach:** * Pros: + More concise and readable code + Less chance of off-by-one errors or array index out-of-bounds issues + Better suited for arrays that need to be iterated over multiple times without re-creating the iterator * Cons: + Can lead to increased garbage collection pauses if not done carefully (using `const` and avoiding unnecessary variable assignments) + Might have performance overhead due to the iterator's internal mechanics 2. **Index-Based Indexing Approach:** * Pros: + Direct access to array elements, which can be faster for simple iteration scenarios + Less chance of garbage collection pauses since no new objects are created during iteration * Cons: + Can lead to more complex and error-prone code due to the need to manage array indices manually + More likely to have off-by-one errors or array index out-of-bounds issues **Library:** There is no explicitly mentioned library in this benchmark, but `forEach` (also known as "for...of" loop) is a built-in JavaScript feature that leverages the V8 engine's iterator implementation. The test is comparing the performance of using the built-in `forEach` method versus traditional for loops. **Special JS Features:** This benchmark does not use any special JavaScript features or syntax beyond the standard language and the provided libraries (V8 engine). **Alternative Benchmarks:** Other alternatives to compare in this type of benchmark could include: * Using other iteration methods, such as `map()` or `reduce()` * Iterating over arrays with different types, like objects or sets * Adding noise to the array elements (e.g., adding random values) to simulate real-world scenarios where performance may degrade due to extra overhead Keep in mind that the choice of alternatives depends on the specific use case and requirements of the benchmark.
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Iterator vs Index for loop
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