Benchmark: FlatMap method vs for loop 31-10-24

Script Preparation code:

var arr = Array(10_000).fill(0);

Tests:

flatMap
arr.flatMap(x => [x, x * 2]);
for loop
const n = arr.length; const acc = new Array(n * 2); for (let i = 0; i < n; i++){ const x = arr[i]; acc[i * 2] = x; acc[i * 2 + 1] = x * 2; }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
flatMap
for loop

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: one month ago)

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36

Browser/OS: Chrome 130 on Windows

View result in a separate tab

Test name	Executions per second
flatMap	3630.4 Ops/sec
for loop	2351.3 Ops/sec

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):

LLMs can make mistakes. Check important info.

The benchmark provided compares the performance of the JavaScript `flatMap` method against a traditional `for` loop for processing an array. The goal is to determine which approach is more efficient when creating a new array that contains each element from the original array alongside a modified version of that element.

### Options Compared
1. **`flatMap` Method**:
   - **Benchmark Definition**: `arr.flatMap(x => [x, x * 2]);`
   - **Description**: This method transforms each element (`x`) of the array `arr` by returning a new array that contains the original element and a second element that is double the original. The resulting arrays from each iteration are then concatenated into a single flattened array.
  
2. **`For` Loop**:
   - **Benchmark Definition**:
     ```javascript
     const n = arr.length;
     const acc = new Array(n * 2);
     for (let i = 0; i < n; i++) {
       const x = arr[i];
       acc[i * 2] = x;
       acc[i * 2 + 1] = x * 2;
     }
     ```
   - **Description**: This approach manually iterates over the array using a `for` loop. It initializes a new array (`acc`) with a length that is twice that of the original array. For each element in the original array, it assigns the element and its doubled value to the appropriate indices in the new array.

### Pros and Cons

#### `flatMap` Method
- **Pros**:
  - **Conciseness**: The syntax is more concise and readable, making it clear that you intend to transform and flatten the array in one operation.
  - **Functional Style**: Aligns well with functional programming paradigms, encouraging immutability.

- **Cons**:
  - **Overhead**: Internally, `flatMap` might have more overhead due to function calls and the creation of intermediate arrays.
  - **Performance**: Can be slower in scenarios where large collections are processed since it involves additional steps of creating and flattening arrays.

#### `For` Loop
- **Pros**:
  - **Performance**: Often faster for large arrays as it eliminates the overhead associated with higher-order functions. The manual control of indices can lead to optimizations.
  - **Control**: Provides granular control over the iteration process and memory usage.

- **Cons**:
  - **Verbosity**: More lines of code and potentially more complex to understand at a glance compared to functional approaches.
  - **Potential for Errors**: Manual handling of indices may lead to off-by-one errors or other bugs if not carefully crafted.

### Considerations
- The choice of method may depend on the context of usage. For smaller arrays or scenarios where readability and maintainability are prioritized, `flatMap` can be preferred. Conversely, for performance-critical paths where array sizes are large, a `for` loop may yield better results.
- Developers should profile both approaches in their own specific cases to determine which is more efficient in their production environment, as the performance can also be influenced by the JavaScript engine and the context in which the code is executed.

### Other Alternatives
- **`map` with `concat`**: Instead of using `flatMap`, one could use `map` along with `concat` to achieve similar results, though it may complicate the readability.
- **`reduce`**: It could also be possible to use the `reduce` method to build the new array iteratively. The reader would have to balance between readability and performance when using `reduce`.
- **Typed Arrays**: If the data is numerical, using typed arrays could lead to better performance characteristics due to contiguous memory allocation.

In summary, the benchmark test offers insights into the performance characteristics of two different approaches to array processing in JavaScript. Understanding the strengths and weaknesses of each method empowers developers to make informed decisions based on their specific application needs.

Related benchmarks:

FlatMap method vs for loop 31-10-24 (version: 0)

Compare the performance of for loop vs flatMap method

Comparing performance of: flatMap vs for loop

Created: one month ago by: Guest

Jump to the latest result

flatMap

for loop

Suite status: <idle, ready to run>

Experimental features:

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model gpt-4o-mini, generated one month ago):