Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

Benchmark Overview

The provided benchmark measures the performance difference between flatMap and two approaches that emulate its behavior: map/flat. The goal is to understand which approach yields the best performance for array flattening operations.

Tested Options

There are three test cases:

1. arr.flatMap(() => [1, 2]): This is the original flatMap method being tested.
2. arr.map(() => [1, 2]).flat(): This is an implementation of map/flat, where the map function generates an array of arrays and then calls flat to flatten it.
3. Array.prototype.flatMap.call(arr, () => [1, 2]): This approach uses Array.prototype.flatMap (a static method) to call the callback function on each element in the array.

Pros and Cons

• arr.flatMap(() => [1, 2]):
  • Pros: Native JavaScript implementation with built-in support for parallel processing.
  • Cons: May have performance variations due to browser optimizations or caching.
• arr.map(() => [1, 2]).flat():
  • Pros: Easy to understand and implement, as it leverages existing map and flat methods.
  • Cons: Involves additional function calls and potential overhead from creating intermediate arrays.
• Array.prototype.flatMap.call(arr, () => [1, 2]):
  • Pros: Similar to the native implementation but uses a static method call for flexibility.
  • Cons: May incur slightly higher overhead due to the additional function call.

Library and Special JS Feature

There is no specific library used in this benchmark. However, it's essential to note that flatMap is a relatively new feature introduced in ECMAScript 2020 (ES10). If you're targeting older browsers or environments, these tests may not be directly applicable.

Other Alternatives

If you need to implement array flattening without using map/flat, other approaches might include:

• Using forEach: Iterate over each element and manually push values into a new array.
• Implementing a custom flatMap method: Define a custom function that uses existing JavaScript features like map, reduce, or forEach.
• Utilizing third-party libraries or polyfills: Some libraries (e.g., Lodash) offer flatten functions, which can be used as alternatives to flatMap.