Benchmark: Array loop vs foreach

Script Preparation code:

   var arr = [];
    for (var i = 0; i < 1000; i++) {
      arr[i] = i;
    }
  
    function someFn(i) {
      return i * 3 * 8;
    }

Tests:

foreach
arr.forEach(function (item){ someFn(item); })
for
const len=arr.length; for (var i = 0; i < len; i++) { someFn(arr[i]); }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
foreach
for

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 years ago)

User agent: Mozilla/5.0 (Unknown; Linux) AppleWebKit/538.1 (KHTML, like Gecko) MAG200 stbapp ver: 4 rev: 734 Mobile Safari/538.1

Browser/OS: Safari on Linux

View result in a separate tab

Test name	Executions per second
foreach	3431.4 Ops/sec
for	3348.8 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 provided benchmark and its results to understand what's being tested.

**Benchmark Overview**

The benchmark compares the performance of two approaches: using `Array.forEach()` and using a traditional `for` loop, both of which iterate over an array and call a function `someFn(i)` on each element.

**Script Preparation Code**

The script preparation code creates an array `arr` with 1000 elements, populating it with values from 0 to 999. It also defines the `someFn(i)` function, which takes an integer `i` as input and returns the result of multiplying `i` by 3 and then by 8.

**Html Preparation Code**

There is no HTML preparation code provided, so we can assume this benchmark focuses solely on JavaScript performance.

**Benchmark Definition**

The benchmark definition consists of two individual test cases:

1. `"arr.forEach(function (item){\r\n  someFn(item);\r\n})"`
2. `"const len=arr.length;\r\nfor (var i = 0; i < len; i++) {\r\n  someFn(arr[i]);\n }"`

These two test cases represent the `foreach` and `for` loop approaches, respectively.

**Library Used**

The benchmark uses the `someFn` function defined in the script preparation code. This function is not a standard JavaScript library but rather a custom function created for this benchmark.

**Special JS Feature/Syntax**

There are no special JavaScript features or syntax used in this benchmark beyond what's commonly found in modern JavaScript. However, it's worth noting that the use of `const` to declare the variable `len` is a relatively recent feature introduced in ECMAScript 2015 (ES6).

**Pros and Cons of Approaches**

1. **Array.forEach()**
	* Pros: more concise and expressive way to iterate over arrays, less prone to errors due to its safer syntax.
	* Cons: may be slower than traditional `for` loops due to the overhead of function calls and potential caching issues.
2. **Traditional for loop**
	* Pros: generally faster and more predictable than `Array.forEach()`, allows for fine-grained control over iteration variables.
	* Cons: more verbose, prone to errors if not handled carefully.

**Other Considerations**

* **Caching**: The benchmark may be affected by caching behavior in the JavaScript engine. For example, if the array is created and modified frequently, caching might lead to slower performance for traditional `for` loops.
* **GC Pressure**: Garbage collection (GC) can impact performance, especially when dealing with large arrays. Both approaches may benefit from optimization strategies that minimize GC pauses.

**Alternatives**

Other alternatives to consider in a benchmark like this could include:

1. **Array.prototype.map()**: Another way to iterate over an array and apply a transformation function.
2. **Set iteration**: If the benchmark is intended for use with sets or other collection types, iterating over them using `for...of` loops or libraries like `lodash.set()` might be more suitable.

Keep in mind that these alternatives may not directly compare to the traditional `Array.forEach()` and `for` loop approaches but could provide additional insight into performance and optimization strategies.

Related benchmarks:

Array loop vs foreach (version: 0)

Comparing performance of: foreach vs for

Created: 5 years ago by: Guest

Jump to the latest result

foreach

for

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):