Benchmark: Loop vs forEach array

Script Preparation code:

var array = new Array(100);

Tests:

Loop
for (var i = 0; i < array.length; i++) { array[i]; }
Loop (extract length)
var l = array.length; for (var i = 0; i < l; i++) { array[i]; }
ForEach
array.forEach(function(item, index) { array[i]; });

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Loop
Loop (extract length)
ForEach

Fastest: N/A

Slowest: N/A

Latest run results:

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

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/105.0.0.0 Safari/537.36

Browser/OS: Chrome 105 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
Loop	78890.0 Ops/sec
Loop (extract length)	158203.2 Ops/sec
ForEach	3528373.5 Ops/sec

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

LLMs can make mistakes. Check important info.

The provided JSON represents a JavaScript microbenchmark that compares three approaches to iterate over an array: traditional `for` loop, loop with extracted length, and `forEach`. Let's break down each option:

**1. Traditional `for` Loop**

This is the most common way to iterate over an array in JavaScript. The benchmark prepares an array of 100 elements and uses a `for` loop to iterate over it, accessing each element individually.

Pros:

* Easy to understand and implement
* Works well for small to medium-sized arrays

Cons:

* Can be slower for large arrays due to the overhead of incrementing the loop variable
* May not be as efficient as other options when working with large datasets

**2. Loop with Extracted Length**

This approach involves extracting the length of the array before the loop, and using that value in the loop condition instead of `array.length`. This can potentially improve performance by reducing the number of iterations.

Pros:

* Can be faster than traditional `for` loops for large arrays
* Reduces unnecessary iterations

Cons:

* May require more memory allocation due to the extracted length variable
* Can be less intuitive for some developers, especially those new to JavaScript

**3. `forEach`**

The `forEach` method is a part of the ECMAScript standard and provides a concise way to iterate over arrays. It takes two arguments: the value of each element and an optional index.

Pros:

* Concise and easy to read
* Works well for small to medium-sized arrays

Cons:

* May not be as efficient as traditional `for` loops or loop with extracted length for large arrays
* Can be slower due to the overhead of function invocation

Now, let's talk about libraries used in the benchmark. There doesn't appear to be any notable library used specifically for this benchmark.

Regarding special JavaScript features or syntax, there are none mentioned in this specific benchmark.

The benchmark provides three test cases:

1. "Loop" - Traditional `for` loop
2. "Loop (extract length)" - Loop with extracted length
3. "ForEach" - `forEach`

The latest benchmark results show the execution frequency per second for each test case on a Chrome 105 browser running on a Mac OS X 10.15.7 system.

Other alternatives to these approaches include:

* Using `Array.prototype.forEach` with an iterator function (not shown in this benchmark)
* Using `for...of` loops (introduced in ECMAScript 2015)
* Using `Map` or other data structures that support iterative processing
* Using just-in-time compilers like V8 or SpiderMonkey to optimize the loop code

These alternatives might offer performance benefits for specific use cases, but may also introduce additional complexity and dependencies.

Related benchmarks:

Loop vs forEach array (version: 2)

Comparing performance of: Loop vs Loop (extract length) vs ForEach

Created: 8 years ago by: Registered User

Jump to the latest result

Loop

Loop (extract length)

ForEach

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):