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

What is tested?

The provided benchmark tests three different approaches to remove duplicates from an array:

1. Using indexOf (index-based method)
2. Using lastIndexOf (index-based method, but with a twist)
3. Using a Set data structure

Each approach is implemented in a separate test case.

Options compared

We have three options being compared:

• Index-based methods: These methods use the indexOf or lastIndexOf functions to find the index of each item in the array. The main difference between these two methods is that lastIndexOf returns the last index of the item, whereas indexOf returns the first index.
• Set data structure: This approach uses a Set data structure to store unique items from the array.

Pros and Cons

Here are some pros and cons for each approach:

• Index-based methods (Using indexOf and Using lastIndexOf):
  • Pros: Simple to implement, widely supported by browsers.
  • Cons: May be slower than other approaches due to the need to iterate over the entire array. Also, lastIndexOf may not work as expected if the item is not found in the beginning of the array.
• Set data structure (Using a Set):
  • Pros: Fast and efficient, as it uses a hash table to store unique items.
  • Cons: Requires additional memory to store the Set data structure, which may be a concern for very large arrays.

Library and purpose

In this benchmark, we can see that two libraries/libraries-like-technologies are used:

• None of these are explicitly mentioned in the json. However, since one of the tests is using a "Set", a similar concept exists: Set (ECMAScript 2015) - which allows to create and store unique values.

Special JS feature or syntax

There is no explicit mention of any special JavaScript features or syntax being used in this benchmark. The implementation focuses on simple, standard JavaScript methods.

Other alternatives

In general, other approaches to remove duplicates from an array include:

• Using a Map data structure (similar to a Set, but with additional capabilities)
• Using a custom sorting algorithm that removes duplicates
• Using a library like Lodash or Underscore.js, which provide various functions for removing duplicates.

However, these alternatives are not being tested in this specific benchmark.

In summary, the MeasureThat.net benchmark tests three approaches to remove duplicates from an array: index-based methods using indexOf and lastIndexOf, and a Set data structure. Each approach has its pros and cons, and we can see that the Set data structure is the fastest and most efficient option in this particular test case.