Let's break down the JavaScript microbenchmark on MeasureThat.net.

Benchmark Definition

The benchmark is designed to compare two approaches for emptying an array in JavaScript: setting the length property of the array to 0, and using the splice() method with its first argument set to 0 and the second argument equal to the length of the array.

Options Compared

1. Set length to zero: This approach sets the length property of the array to 0, effectively emptying it.
2. Splice: This approach uses the splice() method with its first argument set to 0 (the index of the first element) and the second argument set to the length of the array, which removes all elements from the start of the array.

Pros and Cons

• Set length to zero:
  • Pros: Simple, efficient, and widely supported.
  • Cons: May not work as expected in some older browsers or with certain array implementations (e.g., Array.prototype.slice()).
• Splice:
  • Pros: Works consistently across all browsers and array implementations.
  • Cons: More complex and computationally expensive than setting the length property.

Library Usage

There is no explicit library usage in this benchmark. However, it's worth noting that some JavaScript engines (e.g., SpiderMonkey) have internal optimizations for certain operations, which may affect the benchmark results.

Special JS Features or Syntax

None are explicitly mentioned in the benchmark definition or individual test cases.

Other Alternatives

In addition to setting the length property and using splice(), other approaches to emptying an array include:

• Using Array.prototype.length = 0;
• Using arr = new Array(size).fill(0); (a more efficient approach that creates a new array with the desired length)
• Using arr = arr.map((_, i) => { arr[i] = undefined; return i; }); (a more explicit approach using a map function)

Keep in mind that these alternatives may have varying levels of performance, compatibility, and code readability.

I hope this explanation helps!