Benchmark: JS array for test

Tests:

use basic for
const arr = new Array(10000); for (var i = 0; i < arr.length; i++) { var a = arr[i] }
use basic for (start at last)
const arr = new Array(10000); for (var i = arr.length; i >= 0; i--) { var a = arr[i] }
use while (start at last)
const arr = new Array(10000); var i = arr.length while (i--) { var a = arr[i] }
use forEach
const arr = new Array(10000); arr.forEach(v => { var a = v });
use every
const arr = new Array(10000); arr.every(v => { var a = v return true });
use for...in
const arr = new Array(10000); for (var v in arr) { var a = v }
use for...of
const arr = new Array(10000); for(var v of arr) { var a = v }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
use basic for
use basic for (start at last)
use while (start at last)
use forEach
use every
use for...in
use for...of

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 2 years ago)

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 15_5 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.5 Mobile/15E148 Safari/604.1

Browser/OS: Mobile Safari 15 on iOS 15.5

View result in a separate tab

Test name	Executions per second
use basic for	102308.3 Ops/sec
use basic for (start at last)	102653.6 Ops/sec
use while (start at last)	43610.0 Ops/sec
use forEach	4082.8 Ops/sec
use every	5982.5 Ops/sec
use for...in	193343.4 Ops/sec
use for...of	21995.6 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and its various components.

**Benchmark Definition JSON**

The provided JSON represents a JavaScript microbenchmark that tests the performance of different array iteration methods. The `Benchmark Definition` section outlines the specific test case:

* `const arr = new Array(10000);`: Creates an array with 10,000 elements.
* Iteration method: One of six options is chosen for iterating over the array:
	1. Basic for loop (`for (var i = 0; i < arr.length; i++) { ... }`)
	2. Basic for loop starting from the end (`for (var i = arr.length; i >= 0; i--) { ... }`)
	3. While loop starting from the end (`while (i--) { ... }`)
	4. `forEach` method (`arr.forEach(v => { var a = v; });`)
	5. `every` method (`arr.every(v => { var a = v; return true; });`)
	6. For...in loop (`for(var v in arr) { var a = v; }`)
	7. For...of loop (`for (var v of arr) { var a = v; }`)

**Options Comparison**

The six options are compared to measure their performance:

1. **Basic for loops**: These loops use the traditional `i` variable to iterate over the array elements.
2. **While loops**: These loops start from the last element and move towards the first one, using a decrementing counter (`i--`) to access each element.
3. **forEach** method: This method iterates over the array elements without exposing the index variable to the user.
4. **every** method: This method returns `true` if all elements pass the provided test function; otherwise, it returns `false`. The loop is not strictly necessary in this case.
5. **For...in loop**: This loop iterates over the array's property names (i.e., the indices).
6. **For...of loop**: This loop iterates directly over the array elements.

**Pros and Cons of Each Approach**

Here's a brief summary:

1. **Basic for loops**:
	* Pros: Simple, widely supported, and familiar to most developers.
	* Cons: May have performance issues due to index calculation overhead.
2. **While loops**:
	* Pros: Can be faster than basic for loops due to reduced overhead.
	* Cons: Requires manual counter management and can lead to errors if not implemented correctly.
3. **forEach** method:
	* Pros: Concise, readable, and eliminates the need for explicit index calculation.
	* Cons: May incur additional overhead due to the function call and closure mechanism.
4. **every** method:
	* Pros: Simplifies iteration and can be useful for conditional checks.
	* Cons: Returns `true` or `false`, which might not always match the expected behavior.
5. **For...in loop**:
	* Pros: Iterates directly over property names, making it suitable for objects with dynamic indices.
	* Cons: May not be as readable or familiar to developers who are used to array iteration.
6. **For...of loop**:
	* Pros: Concise and modern syntax, iterating directly over array elements without index exposure.
	* Cons: Limited support in older browsers and may lead to errors if not implemented correctly.

**Performance Insights**

The benchmark results show that the performance of each approach varies depending on the specific use case:

* Basic for loops and while loops tend to be slower due to overhead from index calculation and counter management.
* `forEach`, `every`, and For...of loops often outperform basic for loops, especially when considering readability and conciseness.
* The For...in loop performs well when dealing with objects or dynamic indices, but may not be the best choice for arrays.

Keep in mind that these results are specific to this particular benchmark and might not generalize to all scenarios.

Related benchmarks:

JS array for test (version: 0)

Comparing performance of: use basic for vs use basic for (start at last) vs use while (start at last) vs use forEach vs use every vs use for...in vs use for...of

Created: 2 years ago by: Guest

Jump to the latest result

use basic for

use basic for (start at last)

use while (start at last)

use forEach

use every

use for...in

use for...of

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 2 months ago):