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

What is being tested?

MeasureThat.net is testing the performance difference between two approaches: using await with a promise and without it, in this case, with an asynchronous function that returns a value directly (not wrapped in a promise).

Options compared

The two options being compared are:

1. Await on promise: This approach uses await to wait for the completion of a promise returned by another function (foo() -> promise). The promise is then resolved and the result is logged to the console.
2. Await no promise: This approach also uses await, but it's applied directly to an asynchronous function that returns a value, bypassing the need for a promise.

Pros and Cons of each approach

1. Await on promise
   • Pros:
     • More explicit and readable code, as the intent of waiting for a promise is clear.
     • Easier to handle errors using .catch() (although not directly applicable here).
   • Cons:
     • May introduce additional overhead due to the need to create and manage promises.
2. Await no promise
   • Pros:
     • Can be faster, as it avoids the overhead of creating and managing promises.
     • Simplifies the code, making it more concise.
   • Cons:
     • May make the intent of waiting for a value less clear, especially in cases where errors are not properly handled.

Other considerations

When using await with an asynchronous function that returns a value, it's essential to consider how errors will be propagated and handled. In both examples, errors are not explicitly handled, which may lead to unexpected behavior or crashes.

Library usage

In the provided benchmark, no libraries are mentioned as being used. However, if you're using libraries like async/await polyfills or other utilities that provide a way to work with promises in older browsers, their performance impact should be considered when comparing these approaches.

Special JS feature/syntax

There's no special JS feature or syntax being tested here; the focus is on understanding how await works in different scenarios. However, if you're interested in exploring other features like async/await, promise chaining, or generators, MeasureThat.net likely has benchmarks for those as well.

Alternatives

If you're looking to compare performance between await with promises and without them, here are a few alternatives:

• Using then() instead of await: This would simulate the behavior of await on a promise but without the benefits of asynchronous execution.
• Using a callback function: Similar to then(), this approach uses a callback function to handle the result of an asynchronous operation.
• Simulating synchronous execution: You could modify the benchmark to simulate synchronous execution by using Promise.resolve() and then applying the await keyword.

Keep in mind that these alternatives might not accurately represent real-world scenarios, as they don't account for the nuances of asynchronous programming.