Let's break down the provided benchmark and its components.

Benchmark Definition JSON

The benchmark is defined by a JSON object that contains information about the test. The relevant fields are:

• Name: A descriptive name for the benchmark.
• Description: An empty string, indicating no description for this benchmark.
• Script Preparation Code: A JavaScript function createWaitPromise that returns a promise that resolves after a specified number of milliseconds.
• Html Preparation Code: An empty string, indicating no HTML preparation code is needed.

The script defines a global object globalThis and checks if certain properties (SecondsPromise1, SecondsPromise10, and SecondsPromise60) are defined. If any of them are not defined, they are assigned the return value of createWaitPromise with different time intervals (1 second, 10 seconds, or 60 seconds). The comments indicate that these properties are used to create promises that can be waited upon.

Test Cases

The benchmark consists of three test cases:

• Test case 1: Waits for 1 second.
• Test case 2: Waits for 10 seconds.
• Test case 3: Waits for 60 seconds.

Each test case has a Benchmark Definition field that contains the actual JavaScript code to be executed. The code checks if any of the promises are defined and, if not, assigns them using createWaitPromise. The comments indicate that these properties are used to create promises that can be waited upon.

Pros and Cons

The use of promises in this benchmark has both pros and cons:

Pros:

• Promises provide a way to handle asynchronous code in a more elegant and readable manner.
• They allow for better error handling and support for callbacks.

Cons:

• The use of promises might introduce additional overhead due to the creation and resolution of promise objects.
• In this specific case, the benefits of using promises are limited by the fact that the test cases only wait for a short period (1-60 seconds) before resolving.

Library: globalThis

The globalThis object is not a standard library in JavaScript. It's an extension that provides access to global variables and functions on modern browsers. The globalThis object is used here to access the properties SecondsPromise1, SecondsPromise10, and SecondsPromise60.

Special JS Feature: Arrow Functions

The use of arrow functions (() => { ... }) in the benchmark definition code is a feature introduced in ECMAScript 2015 (ES6). It provides a concise way to define small, one-time-use functions.

Other Alternatives

If this benchmark were to be rewritten, other alternatives could include:

• Using setTimeout and clearTimeout instead of promises.
• Using a third-party library like async-promise-executor or bluebird for promise handling.
• Using a testing framework that provides built-in support for async testing.

It's worth noting that the choice of implementation depends on the specific requirements and constraints of the benchmark.