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

What is being tested?

MeasureThat.net is testing two approaches for updating an array: using array.push(...array2) and using the spread operator (array = [...array, ...array2]). The goal of this benchmark is to compare the performance of these two methods in updating an array with a large number of elements.

Options being compared

There are only two options being compared:

1. array.push(...array2): This method uses the spread operator (...) to add all elements from array2 to the end of array. The push() method is called on the resulting array.
2. array = [...array, ...array2]: This method uses the spread operator (...) to create a new array that combines array and array2, and then assigns it back to array.

Pros and Cons of each approach

1. array.push(...array2):
   • Pros: Simple, easy to read, and widely supported.
   • Cons: Can be slower than the spread operator approach due to the overhead of creating a new array in push mode.
2. array = [...array, ...array2]:
   • Pros: Creates a new array with improved performance compared to push() mode, and is generally faster.
   • Cons: Requires understanding of the spread operator syntax and can be less readable.

Library usage

There is no library being used in this benchmark. The test cases only involve JavaScript core functionality.

Special JS feature or syntax

The use of the spread operator (...) is a special JavaScript feature introduced in ECMAScript 2015 (ES6). It allows for creating new arrays by spreading elements from existing arrays.

Other alternatives

Before adopting either approach, it's worth noting that other methods could be used to update an array:

1. array.concat(array2): This method creates a new array and concatenates array and array2. While not as efficient as the spread operator or push mode, it is still widely supported.
2. Array.prototype.splice(): This method updates array in place by replacing a portion of its elements with elements from array2.

The choice of approach ultimately depends on the specific use case and personal preference.

Keep in mind that this benchmark only tests performance, not code readability or maintainability. Depending on the context, other factors might be more important when choosing an array update method.