Benchmark: filter with forEach vs for with if

Script Preparation code:

var arr = [];
for (var i = 0; i < 12345; i++) {
  arr[i] = i;
}

function someFn(i) {
  return (i * 3 * 8 / 1200 * 0.002 / 40 * 0.2);
}

Tests:

forEach
arr.filter(x=>x%2==0).forEach(x=>someFn(x));
for
for (var j = 0; j < arr.length; j++) { const x = arr[i]; if (x%2==0){ someFn(x); } }

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: 2 years ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Browser/OS: Chrome 107 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
forEach	1779.0 Ops/sec
for	375.0 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 explain what is being tested.

**Benchmark Definition**

The benchmark is comparing two approaches to iterate over an array: `forEach` and `for`. The script preparation code generates a large array of numbers and defines a function `someFn` that performs some calculations on each element. The `filter` method is used to filter out odd numbers from the array.

**Options being compared**

The two options being compared are:

1. Using `forEach`: This method iterates over the array, executing the provided callback function for each element.
2. Using a traditional `for` loop: This method uses an explicit index variable (`j`) to iterate over the array elements.

**Pros and Cons of each approach**

**Using `forEach`**

Pros:

* Easier to read and write, as it abstracts away the iteration logic.
* Less error-prone, as the callback function is executed for each element without needing to worry about indexing.

Cons:

* Can be slower due to the overhead of the callback function execution.
* May not be optimized by the browser engine, leading to potential performance variations between different browsers or hardware configurations.

**Using a traditional `for` loop**

Pros:

* Can be faster, as it avoids the overhead of the callback function execution and can be optimized by the browser engine.
* More control over the iteration logic, allowing for custom caching or optimization techniques.

Cons:

* More verbose and error-prone, requiring manual indexing and handling of edge cases.
* May require additional bookkeeping to handle array indices and bounds checking.

**Library usage**

In this benchmark, no specific library is used. However, it's worth noting that some JavaScript libraries (e.g., Lodash) provide optimized versions of the `forEach` method or other iteration algorithms that might impact performance.

**Special JS features or syntax**

There are no special JavaScript features or syntax used in this benchmark. The code relies on standard ECMAScript 5+ functionality.

**Other considerations**

When running benchmarks, it's essential to consider factors like:

* Input size: The larger the input array, the more significant the performance differences between the two approaches.
* Browser and hardware variations: Different browsers or hardware configurations might exhibit varying performance characteristics due to caching, just-in-time (JIT) compilation, or other optimizations.

**Alternatives**

Other alternatives for iterating over arrays include:

1. `for...of` loop (introduced in ECMAScript 2015): This method provides a concise and readable way to iterate over array elements without manual indexing.
2. Array methods like `map`, `reduce`, and `every`: These methods can be used to perform operations on the entire array or subsets of it, potentially offering performance benefits or simplification.
3. Custom iterative functions: Depending on the specific requirements, a custom iterative function might offer better performance or flexibility.

For this particular benchmark, using `for...of` loop instead of `forEach` would likely be a reasonable alternative, as it provides a concise and readable way to iterate over the array elements without introducing additional overhead.

Related benchmarks:

filter with forEach vs for with if (version: 1)

Comparing performance of: forEach vs for

Created: 2 years ago by: Registered User

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):