Benchmark: flatMap() vs map().filter() v2

Script Preparation code:

var arr = [];
var i = 0;

while (i <= 1E6) arr[i] = i++;

Tests:

map().filter()
arr.map(x => x*2).filter(x => x % 3)
flatMap()
arr.flatMap(x => { const next = x*2; return next % 3 ? [next] : []})

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
map().filter()
flatMap()

Fastest: N/A

Slowest: N/A

Latest run results:

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

LLMs can make mistakes. Check important info.

Let's break down the benchmark and analyze what's being tested.

**Benchmark Overview**

The benchmark is comparing two approaches: `map().filter()` and `flatMap()`. The test case involves an array `arr` that's populated with values from 0 to 1 million, using a while loop. The goal is to apply some transformation to the elements of the array.

**Options Compared**

There are two options being compared:

1. **`map().filter()`**: This approach uses the `map()` method to create a new array with the transformed elements, and then uses the `filter()` method to remove any unwanted elements.
2. **`flatMap()`**: This approach uses the `flatMap()` method to transform the elements of the array in a single step.

**Pros and Cons**

Here's a brief analysis of each approach:

1. **`map().filter()`**:
	* Pros:
		+ Can be more predictable and easier to understand for developers who are familiar with this pattern.
		+ Allows for better control over the transformation process.
	* Cons:
		+ May result in more overhead due to the creation of an intermediate array.
		+ Requires two method calls, which can lead to additional function call overhead.
2. **`flatMap()`**:
	* Pros:
		+ More efficient and concise than `map().filter()`, as it applies both transformation and filtering in a single step.
		+ Reduces the number of function calls, potentially leading to better performance.
	* Cons:
		+ May be less intuitive for developers who are not familiar with this pattern.
		+ Can lead to unexpected behavior if not used correctly.

**Library**

The `flatMap()` method is a standard feature in modern JavaScript, introduced in ECMAScript 2019 (ES10). It's designed to simplify the transformation process by applying both mapping and filtering operations in a single step. The library in question is likely built on top of this standard specification.

**Special JS Feature or Syntax**

There are no special features or syntaxes being used in this benchmark. However, it's worth noting that `flatMap()` was introduced in ES10, which may not be supported by older browsers or environments.

**Other Alternatives**

If you wanted to implement this transformation using only built-in methods and loops, you could use a nested loop structure like this:

```javascript
arr.forEach(function(x) {
  var next = x * 2;
  if (next % 3 === 0) {
    arr.push(next);
  }
});
```

This approach would not be as efficient or concise as using `flatMap()`, but it could provide a good learning opportunity for developers who want to understand the underlying mechanics of array transformations.

Overall, the benchmark provides a great opportunity for engineers to compare and contrast two different approaches to array transformation, highlighting the benefits and trade-offs of each method.

Related benchmarks:

flatMap() vs map().filter() v2 (version: 0)

flatMap vs filter map

Comparing performance of: map().filter() vs flatMap()

Created: 4 years ago by: Guest

Jump to the latest result

map().filter()

flatMap()

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

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