I'll explain the benchmark in detail.

What is being tested?

The benchmark tests two approaches to creating an array in JavaScript:

1. EMPTY_ARRAY: Using an existing frozen array (Object.freeze([])).
2. New Array: Creating a new empty array using the Array constructor ([]).

Options compared:

The benchmark compares these two approaches, measuring their performance difference.

Pros and Cons of each approach:

• EMPTY_ARRAY: This approach uses an existing frozen array as a starting point. The pros are:
  • It's more efficient because it reuses memory instead of creating a new one from scratch.
  • It might have better cache locality since it starts with a known, already-allocated array. However, the cons are:
  • It may not be suitable for all use cases where a completely empty array is required (e.g., when the array will be modified frequently).
  • If the original array is large or complex, using EMPTY_ARRAY might not be faster due to overhead of copying its contents.
• New Array: This approach creates an entirely new empty array from scratch. The pros are:
  • It's simple and easy to understand for most developers.
  • It's suitable for use cases where a completely empty array is required (e.g., when the array will be modified frequently). However, the cons are:
  • It can be slower because it creates a new memory allocation from scratch.

Library:

The benchmark uses immer, a library that provides functional programming utilities for JavaScript. In this case, immer.produce is used to create a draft of an object with specific properties.

Immer's purpose:

• Immer helps to create and manipulate data structures in a predictable, thread-safe way.
• It can be useful when dealing with complex, mutable data, like objects or arrays, where concurrent updates need to be handled carefully.

Special JS feature/syntax:

There is no special JavaScript feature or syntax used in this benchmark beyond the use of immer and Object.freeze.

Other alternatives:

If you're interested in exploring alternative approaches for creating empty arrays, here are a few options:

1. Using Array.from() method:

Array.from([]);

2. Using new Array(0) method:

new Array(0);

Both of these methods create an empty array, but they might have slightly different performance characteristics compared to the benchmark's approaches.

Keep in mind that performance differences may be negligible unless you're dealing with extremely large arrays or high-performance applications.