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

Benchmark Definition

The benchmark is testing two different approaches to perform a string manipulation operation:

1. String Split: Using the split() method to split a string into an array of substrings separated by a specified delimiter ('|').
2. Substring: Using the substring() method to extract a part of a string starting from a specified index (lastIndexOf('|')).

Options Compared

The benchmark is comparing two options:

1. Using split(): This option uses the split() method to split the string into an array, and then accesses the last element using pop().
2. Using substring(): This option uses the lastIndexOf() method to find the index of the last occurrence of the delimiter ('|'), and then extracts a part of the string starting from that index using substring().

Pros and Cons

Split()

Pros:

• More intuitive and expressive, as it directly splits the string into an array.
• May be faster if the string is large and doesn't fit in memory as a single substring.

Cons:

• Creates an intermediate array, which can lead to increased memory usage and garbage collection overhead.
• Can be slower due to the overhead of creating the array and accessing its elements.

Substring

Pros:

• More efficient in terms of memory usage, as only a small part of the string is stored in memory.
• May be faster due to the optimized implementation of substring().

Cons:

• Less intuitive and expressive, as it requires finding the index of the delimiter first.
• Can be slower if the string doesn't contain the delimiter or if the index is large.

Library

There is no library used in this benchmark. However, note that some JavaScript engines might provide additional optimization features or built-in methods for these operations (e.g., String.prototype.split() and String.prototype.substring()).

Special JS Feature/Syntax

None are explicitly mentioned in this benchmark. However, it's worth noting that the use of the lastIndexOf() method is a relatively modern JavaScript feature introduced in ECMAScript 2015.

Other Alternatives

In this specific case, there aren't many alternatives to these two approaches. Other options might include:

• Using regular expressions (e.g., s1.match('|')) for string splitting.
• Using the indexOf() method instead of lastIndexOf() for finding the index of a delimiter.

However, it's worth noting that these alternative methods might not be as efficient or expressive as the original two approaches.