Benchmark: flatMap() vs filter().map() 1

Script Preparation code:

var arr = [];
var i = 0;

while (i <= 1E5) arr[i] = i++;

Tests:

filter().map()
arr.filter(x => x % 3).map(x => x/100)
flatMap()
arr.flatMap(x => x % 3 ? x/100 : [])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
filter().map()
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 what's being tested in the provided JSON.

**Benchmark Definition**

The benchmark is comparing two approaches to flatten an array: `flatMap()` and `filter().map()`. The goal is to measure which approach is faster.

**Script Preparation Code**

The script preparation code creates an array `arr` with 100,000 elements, where each element is its index incremented by 1. This will be used as the input for the benchmarking tests.

**Options being compared**

Two approaches are being compared:

1. **`filter().map()`**: This approach uses the `Array.prototype.filter()` method to filter out every third element from the array, and then applies the `Array.prototype.map()` method to each remaining element.
2. **`flatMap()`**: This is a newer method in JavaScript arrays that flattens an array by mapping over it and returning a new flattened array.

**Pros and Cons**

* **`filter().map()`**:
	+ Pros: Widely supported across older browsers, easy to understand and implement.
	+ Cons: Can be slower due to the extra function call and the need to filter out elements before mapping them.
* **`flatMap()`**:
	+ Pros: Efficient, fast, and modern. It avoids the need for extra function calls and can be faster than `filter().map()`.
	+ Cons: Not supported in older browsers (pre-ES6), may require more mental effort to understand due to its concise syntax.

In general, if you're targeting modern browsers and performance is a priority, `flatMap()` might be the better choice. However, if you need to support older browsers or prefer a more straightforward approach, `filter().map()` can still deliver good results.

**Library**

There are no specific libraries being used in this benchmarking test. The tests only rely on standard JavaScript array methods and syntax.

**Special JS feature**

The use of `flatMap()` is a newer JavaScript feature introduced in ES6. If you're targeting browsers that don't support ES6 or later, you'll need to consider alternative approaches.

**Alternatives**

If you want to test other approaches, here are some alternatives:

* **`reduce()`**: You can flatten an array using the `Array.prototype.reduce()` method. This approach would require a callback function to handle each element.
* **Manual looping**: If performance is critical, you could use manual looping to iterate over the array and build the flattened result. This approach would be more verbose but might offer better control.

Keep in mind that benchmarking JavaScript code can be complex due to browser-specific optimizations and other factors. Always consider the specific requirements of your project when choosing a testing approach.

Related benchmarks:

flatMap() vs filter().map() 1 (version: 0)

flatMap vs filter map

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

Created: 2 years ago by: Guest

Jump to the latest result

filter().map()

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):