Let's break down the provided JSON and benchmark preparation code to understand what is being tested.

What is being tested?

MeasureThat.net is testing the performance of two JavaScript operations: array.push(123) and array.splice(array.length, 0, 123). These operations are commonly used in array manipulation scenarios.

Options compared

The provided benchmark compares two approaches to perform these operations:

1. array.push(123): This approach uses the push() method to add an element to the end of the array.
2. array.splice(array.length, 0, 123): This approach uses the splice() method to insert a new element at the beginning of the array.

Pros and Cons

array.push(123):

Pros:

• Simple and intuitive implementation
• Fast execution, as it only needs to update the internal state of the array

Cons:

• May cause intermediate array resizing, leading to slower performance in large arrays
• Does not allow for efficient insertion at arbitrary positions

array.splice(array.length, 0, 123):

Pros:

• Allows for efficient insertion at arbitrary positions
• Can be more efficient than push() when dealing with large arrays or inserting elements at the beginning

Cons:

• More complex implementation, which may lead to slower execution and increased overhead
• May require temporary arrays or other optimization techniques to achieve good performance

Other considerations

Both approaches have limitations:

• In both cases, modifying an array can be a costly operation, especially for large datasets.
• These operations do not take into account modern JavaScript optimizations, such as lazy allocation or caching.

Library and special JS features used in the test case

The provided benchmark code does not explicitly mention any libraries. However, it uses native JavaScript methods (push() and splice()) that are part of the ECMAScript standard.

Special JS feature explanation (not applicable)

There is no special JavaScript feature or syntax mentioned in this benchmark.