Benchmark: forEach with filter 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);
}

var sumForEach = 0,
  sumReduce = 0,
  sumMap = 0,
  sumFilter = 0,
  sumFor = 0;

Tests:

forEach
arr.filter(x=>x%2==0).forEach(x=>x+1);
for
for (var j = 0; j < arr.length; j++) { if (arr[i]%2==0){ arr[i]+1; } }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
forEach
for

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated 29 days ago):

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what is being tested, the different options compared, their pros and cons, and other considerations.

**Benchmark Overview**

The benchmark measures the performance of two approaches to iterate over an array: `forEach` with a filter, and `for` loop with an `if` statement.

**Script Preparation Code**

The script preparation code generates an array of 12345 elements, where each element is a unique number. It also defines a function `someFn` that takes an integer as input and returns a calculated value.

**Benchmark Definition json**

There are two benchmark definitions:

1. `"arr.filter(x=>x%2==0).forEach(x=>x+1);"`
This code filters the array to only include even numbers, then iterates over the remaining elements using `forEach`, incrementing each element by 1.
2. `"for (var j = 0; j < arr.length; j++) {\r\n  if (arr[i]%2==0){\r\n  arr[i]+1;\r\n  }\r\n}"`

The first code uses the modern `filter` and `forEach` methods, while the second code uses a traditional `for` loop with an `if` statement.

**Library Usage**

Both benchmark definitions use the built-in JavaScript array methods (`filter` and `forEach`) which are part of the ECMAScript standard. These methods are implemented by the browser's JavaScript engine (in this case, Chrome).

**Special JS Features/Syntax**

None mentioned explicitly, but it's worth noting that modern JavaScript benchmarks often focus on performance optimizations using modern features like arrow functions, template literals, and array methods.

**Performance Comparison**

The benchmark compares the performance of two approaches:

1. `forEach` with a filter
2. Traditional `for` loop with an `if` statement

**Pros and Cons:**

* **Modern approach (`forEach` with filter)**:
	+ Pros:
		- More concise and readable code
		- Fewer lines to maintain
		- Less chance of errors due to fewer manual iteration variables
	+ Cons:
		- May have performance overhead due to the modern method's implementation
		- Requires support for modern JavaScript features (e.g., arrow functions)
* **Traditional approach (`for` loop with `if` statement)**:
	+ Pros:
		- Often faster due to less overhead from modern methods
		- More familiar and easier to understand for some developers
	+ Cons:
		- Longer code length, increasing the chance of errors
		- More manual iteration variables can lead to bugs

**Other Considerations**

* **Browser implementation**: The benchmark's performance may vary depending on the browser's JavaScript engine implementation. Chrome 107 is used in this case.
* **Array size and complexity**: The array size (12345) and element complexity (a simple number) might not accurately represent real-world scenarios, where arrays can contain more complex data structures or larger sizes.

**Alternatives**

If you're looking for alternative approaches to iterate over an array, consider:

* `for...of` loop: A modern loop that's similar to `forEach`, but with a few key differences.
* `map()`: Creates a new array by applying a transformation function to each element.
* `reduce()`: Applies a reduction function to each element of the array.

Note that these alternatives may have different performance characteristics or use cases, and should be evaluated on a case-by-case basis.

Latest run results:

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

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36

Browser/OS: Chrome 107 on Linux

View result in a separate tab

Test name	Executions per second
forEach	37575.7 Ops/sec
for	966.3 Ops/sec

Related benchmarks:

forEach with filter vs for with if (version: 0)

Comparing performance of: forEach vs for

Created: 2 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 29 days ago):