Let's break down the provided benchmark definition and test cases.

Benchmark Definition

The benchmark defines two functions: runSwitch and LUT[input]. The latter is likely a typo, but it appears to be a lookup table (LUT) with key-value pairs, where each value is set to true.

Here's what the script preparation code shows:

• var runSwitch = input => { ... }: This defines an anonymous function named runSwitch that takes an input parameter. The function contains a switch statement that returns true for each of the 10 cases (e.g., 'one', 'two', etc.). This suggests that the benchmark is testing the performance of the switch statement in JavaScript.
• var LUT = { ... }: This defines an object (LUT) with key-value pairs, where each key is a string and each value is set to true. The purpose of this lookup table is unclear without more context.

Options Compared

The benchmark compares the performance of two approaches:

1. Switch Statement: This option uses the switch statement in the runSwitch function.
2. Lookup Table (Map): This option uses the LUT[input] expression, which appears to be a lookup operation using the object LUT.

Pros and Cons of Each Approach

• Switch Statement:
  • Pros:
    • More readable code
    • Can handle more complex cases with multiple branches
  • Cons:
    • May be slower than lookup tables for large numbers of keys
• Lookup Table (Map):
  • Pros:
    • Fast performance, especially for large datasets
    • Memory-efficient
  • Cons:
    • Less readable code
    • Requires manual management of key-value pairs

Library and Special JS Features

There are no libraries explicitly mentioned in the benchmark definition. However, the LUT[input] expression uses a feature called "computed property access" (introduced in ECMAScript 2015) to dynamically access properties of an object using a string as the key.

Other Considerations

• The benchmark uses Chrome 69 as the browser, which may limit its applicability to other browsers or versions.
• The benchmark is run on a desktop platform with Mac OS X 10.13.6, which may also affect its generality.

Alternatives

Some alternative approaches could be considered:

1. Using Object.keys() and Array.prototype.forEach(): This approach would involve iterating over the keys of the LUT object using Object.keys(), and then applying a callback function to each key using Array.prototype.forEach(). While this approach avoids the computed property access, it may be slower than the lookup table approach.
2. Using a library like Lodash's get(): This approach would involve using a library like Lodash that provides a get() function for accessing properties of an object dynamically. However, this would require including an external dependency and may not offer significant performance benefits.

In summary, the benchmark definition tests the performance of two approaches: the switch statement in JavaScript and a lookup table (map) using computed property access. The choice between these approaches depends on factors like code readability, performance requirements, and the specific use case.