Let's break down what's being tested in this benchmark.

Benchmark Definition

The benchmark is testing the performance difference between two approaches: concatenating arrays using the concat() method and spreading an array using the spread operator (...).

Options Compared

There are two options compared:

1. Concatenation: This approach uses the concat() method to concatenate two arrays, [a] and [b]. The resulting array is stored in variable c.
2. Spreading: This approach uses the spread operator (...) to create a new array by spreading the elements of both input arrays, [a] and [b]. The resulting array is also stored in variable c.

Pros and Cons

• Concatenation:
  • Pros: Simple and easy to understand. It's been around for a long time and has good browser support.
  • Cons: Can be slower than spreading, especially when dealing with large arrays.
• Spreading:
  • Pros: Generally faster than concatenation, as it avoids creating an intermediate array.
  • Cons: Requires modern JavaScript features (ECMAScript 2015+) and may not work in older browsers.

Library Used

There is no library used in this benchmark. The tests only use built-in JavaScript features.

Special JS Feature/ Syntax

There are no special JavaScript features or syntax used beyond what's required for the two options being compared.

Other Alternatives

If the spread operator were not available, an alternative could be using Array.prototype.push() to concatenate arrays:

var c = []; c.push.apply(c, a); c.push.apply(c, b);

Another option would be using Array.prototype.reduce() or Array.prototype.forEach() to achieve similar results.

It's worth noting that in modern JavaScript, the spread operator is often preferred over concatenation because of its efficiency and simplicity.

Benchmark Preparation Code

The provided benchmark preparation code is empty. Typically, this code would include any necessary setup or initialization to prepare the test environment.

Latest Benchmark Result

The latest benchmark result shows the performance characteristics of both options for a specific browser (Firefox 83) on a desktop device running Ubuntu. The results indicate that spreading is generally faster than concatenation, which aligns with expectations based on the pros and cons discussed earlier.