Benchmark: flatMap vs reduce with desctructuring vs reduce without desctructuring

Script Preparation code:

var arr = Array(10_000).fill(0)

Tests:

reduce with concat without destructuring
arr.reduce((acc, x) => acc.concat(x).concat(x), [])
flatMap
arr.flatMap(x => [x, x])
reduce with concat with destructuring
arr.reduce((acc, x) => [...acc, x, x], [])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
reduce with concat without destructuring
flatMap
reduce with concat with destructuring

Fastest: N/A

Slowest: N/A

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

LLMs can make mistakes. Check important info.

Let's break down the provided benchmark JSON and explain what is being tested.

**Benchmark Definition**

The benchmark defines three test cases, each comparing different approaches to concatenate arrays in JavaScript:

1. `arr.reduce((acc, x) => acc.concat(x).concat(x), [])`: This approach uses the `reduce()` method with a callback function that concatenates `x` twice and returns the result.
2. `arr.flatMap(x => [x, x])`: This approach uses the `flatMap()` method to flatten an array of arrays into a single array.
3. `arr.reduce((acc, x) => [...acc, x, x], [])`: This approach uses the spread operator (`...`) to create a new array and concatenate `x` twice.

**Options Compared**

The benchmark compares three options:

1. **Reduce with concat without destructuring**: Uses the `concat()` method to concatenate arrays.
2. **flatMap**: Uses the `flatMap()` method to flatten an array of arrays into a single array.
3. **Reduce with concat with destructuring**: Uses the spread operator (`...`) to create a new array and concatenate `x` twice.

**Pros and Cons**

Here are some pros and cons for each approach:

1. **Reduce with concat without destructuring**:
	* Pros: Simple, widely supported, and easy to understand.
	* Cons: Can be slow, especially for large arrays, since it creates a new array on each iteration.
2. **flatMap**:
	* Pros: Fast, efficient, and scalable, as it avoids creating intermediate arrays.
	* Cons: Less intuitive than the other approaches, may require more code to achieve the same result.
3. **Reduce with concat with destructuring**:
	* Pros: Can be faster than `concat()` since it avoids creating intermediate arrays, but still requires JavaScript knowledge.
	* Cons: May not be as widely supported or well-known as the other approaches.

**Libraries and Special JS Features**

None of the test cases explicitly use any libraries beyond what's built into JavaScript. However, the `flatMap()` method is a part of ECMAScript 2019 (ES2020) standard, which may require modern browsers to execute correctly.

**Test Case Explanations**

1. The first test case uses `reduce()` with concatenation and returns a new array.
2. The second test case uses `flatMap()`, which takes an iterable as input and flattens it into a single array.
3. The third test case uses `reduce()` again, but this time with the spread operator to create a new array.

**Alternatives**

Other approaches to concatenate arrays in JavaScript include:

1. Using the `Array.prototype.push()` method to add elements to an array.
2. Utilizing libraries like Lodash or Ramda for functional programming utilities.
3. Leveraging built-in methods like `Array.from()` and `Set.prototype.add()` for more efficient results.

Keep in mind that these alternatives may have different performance characteristics, ease of use, or code readability compared to the approaches tested in this benchmark.

Latest run results:

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

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36 Edg/126.0.0.0

Browser/OS: Chrome 126 on Windows

View result in a separate tab

Test name	Executions per second
reduce with concat without destructuring	1.4 Ops/sec
flatMap	4694.7 Ops/sec
reduce with concat with destructuring	18.9 Ops/sec

Related benchmarks:

flatMap vs reduce with desctructuring vs reduce without desctructuring (version: 0)

Comparing performance of: reduce with concat without destructuring vs flatMap vs reduce with concat with destructuring

Created: one year ago by: Guest

Jump to the latest result

reduce with concat without destructuring

flatMap

reduce with concat with destructuring

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

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