Let's dive into the world of JavaScript microbenchmarks.

What is being tested?

The provided benchmark tests three ways to concatenate or add elements to an array in JavaScript:

1. Array.prototype.concat(): This method creates a new array by copying all elements from one array and then adding additional arrays or elements.
2. The spread operator (...): Introduced in ECMAScript 2015 (ES6), this syntax allows you to expand an array into a list of arguments, creating a new array.
3. Array.prototype.push(): This method adds one or more elements to the end of an existing array.

Options comparison

Here's a brief overview of each option and their pros and cons:

1. Array.prototype.concat():
   • Pros: Simple, widely supported, and easy to use.
   • Cons: Creates a new array every time it's called, which can be inefficient for large datasets.
2. Spread operator (...):
   • Pros: Efficient, modern syntax, and flexible (can be used with arrays or objects).
   • Cons: May require JavaScript version 6+ to work, and some older browsers might not support it.
3. Array.prototype.push():
   • Pros: Efficient for large datasets, as it only adds elements to the existing array.
   • Cons: Can be slower than spread operator for small datasets, as it involves more memory allocation.

Library usage

None of the tested options rely on external libraries.

Special JavaScript features/syntax

The spread operator (...) is a relatively new feature introduced in ECMAScript 2015 (ES6). It allows you to expand an array or object into a list of arguments, creating a new array. This syntax was adopted by modern browsers and JavaScript engines.

Other alternatives

While not explicitly tested in the provided benchmark, other alternatives for concatenating or adding elements to arrays include:

• Array.prototype.slice() followed by Array.prototype.concat()
• Using a library like Lodash's concat function
• Using a custom implementation with a loop

Keep in mind that these alternatives might not be as efficient or concise as the tested options.

Benchmark result interpretation

The benchmark results show the execution times for each test case on a Chrome 107 browser running on a Mac OS X 10.15.7 system. The order of execution times is:

1. Array.prototype.push(): ~35 seconds per second
2. Spread operator (...): ~31 seconds per second
3. Array.prototype.concat(): ~12 seconds per second

This suggests that, in this specific test case and configuration, the spread operator is the fastest option, followed closely by Array.prototype.push().