Benchmark: flatMap() vs map(...).flat()

Script Preparation code:

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

Tests:

map(...).flat()
arr.map(x => [x % 3]).flat()
flatMap()
arr.flatMap(x => [x % 3])

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

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

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_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36

Browser/OS: Chrome 116 on Mac OS X 10.15.7

View result in a separate tab

Test name	Executions per second
map(...).flat()	115.8 Ops/sec
flatMap()	126.5 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 its test cases.

**Benchmark Overview**

The benchmark compares two approaches for flattening an array: `flatMap()` vs `map() + .flat()`. The goal is to determine which approach is faster.

**Test Cases**

There are only two test cases:

1. `arr.map(x => [x % 3]).flat()`: This test case uses the `map()` function to apply a transformation (`x % 3`) to each element of the array, and then calls `flat()` on the resulting array.
2. `arr.flatMap(x => [x % 3])`: This test case uses the `flatMap()` function to flatten the array directly.

**Library Used**

In both test cases, no external library is used beyond what's built-in to JavaScript. The `map()` and `flatMap()` functions are part of the ECMAScript standard.

**Special JS Features or Syntax**

The benchmark does not use any special JavaScript features or syntax that requires additional explanation. Both `map()` and `flatMap()` are widely supported by modern browsers and Node.js environments.

**Pros and Cons of Approaches**

1. **`map() + .flat()`**:
	* Pros:
		+ Can be more intuitive for developers who are familiar with the `flat()` method.
		+ Allows for easier debugging, as the transformed array is visible in the console or debugger.
	* Cons:
		+ Creates an intermediate array, which can lead to higher memory usage and slower performance compared to `flatMap()`.
2. **`flatMap()`**:
	* Pros:
		+ Flattens the array directly, without creating an intermediate array.
		+ Can be faster in terms of execution time, especially for large arrays.
	* Cons:
		+ May require more complex code or additional libraries to achieve the same result as `map() + .flat()`.

**Other Alternatives**

If you need to flatten an array and want to explore other alternatives, consider using:

1. **`Array.prototype.flat()` (ES6)**: This is a built-in method that flattens an array without creating an intermediate array.
2. **`Array.prototype.reduce()`**: You can use `reduce()` to concatenate arrays, but it requires more code and may not be as efficient as `flatMap()`.
3. **Third-party libraries or polyfills**: Some libraries (e.g., Lodash) provide a `flatten()` function that can flatten an array without creating an intermediate array.

**Benchmark Results**

The benchmark results show the performance of each test case on a specific machine running Chrome 116 on Mac OS X 10.15.7. The first result (`flatMap()`) is slightly faster than the second result (`map() + .flat()`), indicating that `flatMap()` may be the preferred approach for this particular use case.

Related benchmarks:

flatMap() vs map(...).flat() (version: 0)

flatMap vs map and then flat()

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

Created: one year ago by: Guest

Jump to the latest result

map(...).flat()

flatMap()

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):