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

Script Preparation code:

var arr = [];
var i = 0;

while (i <= 1E5) arr[i] = {
    num: [1, i++]
};

Tests:

map().flat()
arr.map(x => x.num).flat()
flatMap()
arr.flatMap(x => x.num)

Historical Performance Data aggregated from 11 community runs

Desktop Results:

Chrome 11 runs

map().flat()

313/s

flatMap()

281/s

Fastest: map().flat() (1.1x faster)

View exact numbers

✓ map().flat(): 313 ops/sec
• flatMap(): 281 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

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: 22 days ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/147.0.0.0 Safari/537.36 Edg/147.0.0.0

Browser/OS: Chrome 147 on Windows

View result in a separate tab

map().flat()

140/s

flatMap()

128/s

View exact numbers

Test name	Executions per second
✓ map().flat()	140 Ops/sec
flatMap()	128 Ops/sec

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

LLMs can make mistakes. Check important info.

I'd be happy to help explain the provided benchmark.

**Benchmark Overview**

The benchmark is designed to compare two approaches: `flatMap()` and chaining `map()` with `flat()`. The test creates an array of objects, where each object has a property `num` containing an array. The goal is to measure the performance difference between these two approaches.

**Options Compared**

The two options being compared are:

1. **flatMap()**: This method calls the provided callback function once for each element in the array and returns an array of the results.
2. **map().flat()**: This approach first applies the `map()` method to the array, which creates a new array with the transformed elements, and then applies the `flat()` method to flatten the resulting array.

**Pros and Cons**

1. **flatMap()**:
	* Pros: More concise and expressive, as it combines two operations into one.
	* Cons: Might be less readable for complex transformations, as the callback function needs to handle both mapping and flattening.
2. **map().flat()**:
	* Pros: Easier to understand and maintain, especially for complex transformations, as each operation is clearly separated.
	* Cons: More verbose and may not be as efficient due to the overhead of calling two separate methods.

In general, `flatMap()` can provide better performance when the transformation involves both mapping and flattening, while `map().flat()` might be more readable but potentially slower.

**Library Used**

The benchmark uses the built-in JavaScript `Array` prototype methods: `flatMap()`, `map()`, and `flat()`.

**Special JS Feature or Syntax**

No special features or syntax are used in this benchmark. However, it's worth noting that some older browsers might not support `flatMap()`, which would require falling back to the `map().flat()` approach.

**Alternative Approaches**

Other alternatives to consider when working with arrays and transformations include:

1. **Using a library**: Depending on the specific requirements, libraries like Lodash or Ramda can provide more concise and expressive ways to perform common array operations.
2. **Looping**: For simple cases, using a traditional loop might be faster than applying an array method, but this approach can lead to less readable code.
3. **Using a different data structure**: If the transformation involves complex logic, considering alternative data structures like objects or graphs might provide better performance.

Keep in mind that benchmarking results may vary depending on the specific use case and JavaScript engine being used.

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

flatMap vs map and flat

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

Created: 4 years ago by: Guest

Go to the latest result

map().flat()

flatMap()

Historical Performance Data aggregated from 11 community runs

Desktop Results:

Chrome 11 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

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

flatMap vs map and flat

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

Created: 4 years ago by: Guest

Go to the latest result

map().flat()

flatMap()

Historical Performance Data aggregated from 11 community runs

Desktop Results:

Chrome 11 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

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

Related benchmarks

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