Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

The provided benchmark measures the performance difference between two approaches to concatenate arrays in JavaScript: using Array.prototype.concat() and the spread operator (...).

What is tested?

The benchmark tests how fast each approach can concatenate two large arrays (1000 elements) created with Array(1000).fill('a') and Array(1000).fill('b').

Options compared:

1. Array.prototype.concat():
   • This method takes two or more arrays as arguments and returns a new array containing all the elements from each input array.
   • It's a built-in method in JavaScript, making it widely supported across different browsers and environments.
2. Spread operator (...):
   • This syntax was introduced in ECMAScript 2015 (ES6) and allows you to expand an iterable (like an array) into individual elements.
   • It's a concise way to create a new array with elements from multiple sources.

Pros and cons:

1. Array.prototype.concat():
   • Pros:
     • Widely supported across different browsers and environments.
     • Can handle large arrays efficiently.
   • Cons:
     • Creates a new array, which can lead to increased memory usage for large input sizes.
     • May not be as performant as other approaches (see below).
2. Spread operator (...):
   • Pros:
     • More concise and readable than concat().
     • Reduces memory usage compared to creating a new array with Array.prototype.concat().

Library/dependencies:

None mentioned in the benchmark definition or test cases.

Special JavaScript features/syntax:

The spread operator (...) is a relatively recent feature introduced in ECMAScript 2015 (ES6). It's widely supported across modern browsers, but may not work in older versions.

Other alternatives:

1. Array.prototype.push() and Array.prototype.length:
   • You could concatenate two arrays by pushing elements from one array into another using push().
2. Array.prototype.forEach() or Array.prototype.map():
   • These methods can be used to concatenate two arrays, but might be less efficient due to their side effects (e.g., modifying the original array).

Keep in mind that these alternatives may have varying degrees of performance and readability compared to the spread operator.

Now, if you're curious about how MeasureThat.net generates benchmark results or what else is tested on the website, feel free to ask!