Benchmark: flatMap (that filters) and forEach with (conditional) push

Script Preparation code:

var arr = Array(10_000).map((_, i) => i)

Tests:

flatMap
const out = arr.flatMap(x => x % 3 === 0 ? [x, x]: []);
forEach with conditional push
const out = []; arr.forEach(x => (x % 3 === 0) && out.push(x));

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
flatMap
forEach with conditional push

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 11 months ago)

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36

Browser/OS: Chrome 119 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
flatMap	9884.0 Ops/sec
forEach with conditional push	52939.0 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's being tested.

**Benchmark Definition**

The benchmark is designed to compare the performance of two different approaches:

1. `flatMap` (that filters) and
2. `forEach with conditional push`

**Options Compared**

In the first test case, `flatMap`, the function takes an array as input and returns a new array after applying a mapping transformation. The transformation consists of taking each element in the input array and checking if it meets a certain condition (`x % 3 === 0`). If the condition is met, the element is included in the resulting array; otherwise, it's not.

In the second test case, `forEach with conditional push`, the function iterates over the input array using `forEach` and pushes elements that meet the same condition into a new array (`out`).

**Pros and Cons**

1. **flatMap**
	* Pros:
		+ More concise and expressive code
		+ Often preferred for performance because it can short-circuit iterations and reduce memory allocations.
	* Cons:
		+ Might not be as intuitive or easy to read for developers unfamiliar with the syntax.
		+ Can lead to unexpected behavior if not used carefully (e.g., when dealing with null or undefined values).
2. **forEach with conditional push**
	* Pros:
		+ More flexible and adaptable to different use cases
		+ Often preferred by developers who are more familiar with the `forEach` method.
	* Cons:
		+ Less concise and may result in slower performance due to the repeated push operation.

**Library Usage**

None of the provided benchmark test cases explicitly uses any external libraries. However, it's worth noting that some JavaScript engines (e.g., V8) have optimized implementations for `flatMap` that can provide better performance compared to using `forEach` with a conditional push.

**Special JS Feature or Syntax**

There are no special JavaScript features or syntax used in the provided benchmark test cases. The code is written in standard JavaScript and follows the ECMAScript 2022 specification.

**Other Alternatives**

If you wanted to compare alternative approaches, here are some possibilities:

1. Using `Array.prototype.filter` instead of `flatMap`
2. Implementing a custom iteration using a `for...of` loop
3. Comparing performance with other array methods (e.g., `map`, `reduce`) or iteration techniques (e.g., using a `while` loop)
4. Including additional optimizations, such as parallelizing the iteration or using a Just-In-Time (JIT) compiler

Please note that these alternatives would require modifying the benchmark test cases to accommodate the new approaches.

In summary, the provided benchmark compares the performance of two common array methods: `flatMap` and `forEach with conditional push`. While both approaches have their pros and cons, `flatMap` is often preferred for its concise syntax and potential performance benefits.

Related benchmarks:

flatMap (that filters) and forEach with (conditional) push (version: 0)

Checking if cases that flatMaps actually filters and maps agains a condition push using forEach

Comparing performance of: flatMap vs forEach with conditional push

Created: 11 months ago by: Guest

Jump to the latest result

flatMap

forEach with conditional push

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):