Benchmark: Array slice.forEach vs for loop

Script Preparation code:

var data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];

Tests:

slice
data.slice(3, 8).forEach(x => x + 1);
push
for (var i = 3; i < 8; i++) { data[i] + i }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
slice
push

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one year ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:137.0) Gecko/20100101 Firefox/137.0

Browser/OS: Firefox 137 on Mac OS X 10.15

View result in a separate tab

Test name	Executions per second
slice	60421192.0 Ops/sec
push	374583808.0 Ops/sec

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark and explain what's being tested, compared options, pros and cons of those approaches, library usage, special JavaScript features, and alternatives.

**Benchmark Overview**

The benchmark compares two approaches to iterate over a subset of an array:

1. **Array `slice()` with `forEach()`**: This approach creates a new slice of the original array (from index 3 to 8) and then uses the `forEach()` method to execute a callback function on each element.
2. **Classic `for` loop**: This approach uses a traditional `for` loop to iterate over the desired subset of the array, incrementing an index variable (`i`) until it reaches the end of the slice.

**Comparison Options**

The benchmark compares these two approaches for iterating over a specific subset of the `data` array ( indices 3 to 8).

**Pros and Cons of each approach:**

1. **Array `slice()` with `forEach()`**:
	* Pros:
		+ concise and expressive code
		+ eliminates the need for manual index management
	* Cons:
		+ creates a new array slice, which can be memory-intensive
		+ may incur additional overhead due to function calls and stack management
2. **Classic `for` loop**:
	* Pros:
		+ more control over indexing and iteration
		+ potentially faster since it avoids creating an extra array
	* Cons:
		+ requires manual index management, which can lead to errors
		+ less concise and expressive code

**Library Usage**

The `forEach()` method is a built-in JavaScript library function that applies a callback function to each element of an array.

**Special JavaScript Features**

There are no special JavaScript features mentioned in this benchmark. Both approaches rely on standard JavaScript syntax and features.

**Alternatives**

Other alternatives for iterating over subsets of arrays include:

1. **`map()`**: While not directly applicable to simple iteration, `map()` can be used with a callback function to create a new array.
2. **`filter()`**: Similar to `forEach()`, but returns a new array with elements that pass the test.
3. **Low-level indexing and iteration**: Other approaches might use low-level indexing (e.g., using `Array.prototype.subarray()`) or custom iteration logic.

**Benchmark Preparation Code**

The preparation code initializes an array `data` with 10 elements, which is used as the basis for the benchmark.

**Individual Test Cases**

Each test case represents a single benchmark definition:

1. **"slice"`**:
	* The benchmark definition: `data.slice(3, 8).forEach(x => x + 1)`
	* This code creates a new slice of `data` from index 3 to 8 and applies the callback function `x => x + 1` to each element in the slice.
2. **"push"`**:
	* The benchmark definition: `for (var i = 3; i < 8; i++) {\r\n  data[i] + i\r\n}`
	* This code uses a traditional `for` loop to iterate over the desired subset of `data`, incrementing an index variable (`i`) and applying the expression `data[i] + i` to each element.

These test cases will be executed on the provided browser version (Chrome 123) with specified platform, device type, and operating system. The benchmark result is the raw execution time per second for each test case.

Related benchmarks:

Array slice.forEach vs for loop (version: 0)

Comparing performance of: slice vs push

Created: 5 years ago by: Guest

Jump to the latest result

slice

push

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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