Let's break down the provided benchmark and explain what's being tested.

What is tested?

The benchmark compares the performance of two approaches:

1. Lodash's _.union method
2. JavaScript's native Set() constructor

Both approaches are used to merge two arrays, a and b, into a new array with unique elements.

Options compared:

• Lodash's _.union: This approach uses the _.union function from Lodash, which merges two arrays into a new array with duplicate values removed.
• Native Set() constructor: This approach uses the JavaScript native Set() constructor to merge two arrays into a set, and then converts the set back into an array.

Pros and cons of each approach:

• Lodash's _.union:
  • Pros:
    • Easy to use and readable
    • Provides a consistent API for merging arrays
  • Cons:
    • May not be optimized for performance, especially for large datasets
    • Requires including an additional library (Lodash)
• Native Set() constructor:
  • Pros:
    • Optimized for performance, especially for large datasets
    • Built-in and doesn't require any additional libraries
  • Cons:
    • May be less readable due to the need to convert back and forth between sets and arrays
    • Requires understanding of set operations

Library: Lodash

Lodash is a popular JavaScript utility library that provides a collection of functional programming helpers, including the _.union function. The library includes over 100 functions for tasks like array manipulation, object transformation, and more.

Special JS feature/syntax: None mentioned in this benchmark

However, it's worth noting that set operations are a fundamental concept in JavaScript and can be used to perform various operations on data structures, such as removing duplicates or performing union/intersection/difference operations.

Other alternatives:

• Other approaches for merging arrays might include using Array.prototype.concat(), Array.prototype.filter(), or other custom solutions. However, these options are generally less efficient than the native Set() constructor approach.
• Some alternative libraries, like Ramda, might provide optimized implementations of array merging functions.