Let's dive into the world of JavaScript microbenchmarks.

Benchmark Overview

The benchmark is designed to compare three different ways to append an array array2 to another array array. The three methods being compared are:

1. Using push() with spread syntax (...)
2. Using spread syntax ([...array, ...array2])
3. Using the concat() method

What is tested

The benchmark measures the performance of each method on a large array (10 elements) and its equivalent larger array (20 elements). The test cases are designed to capture the overhead introduced by each method.

Options compared

• Push with spread syntax: This method uses the spread operator (...) to create a new array by concatenating array and array2. It's a concise way to append elements to an array.
  • Pros: Easy to read, concise, efficient.
  • Cons: May incur additional overhead due to the creation of a new array object.
• Spread syntax: This method uses the spread operator ([...array, ...array2]) to create a new array by concatenating array and array2. It's a more explicit way to append elements to an array.
  • Pros: More control over the resulting array, efficient.
  • Cons: May be less readable than the push with spread syntax method.
• Concat(): This method uses the concat() method to concatenate array and array2. It's a traditional way to merge arrays.
  • Pros: Well-established, easy to understand.
  • Cons: May incur additional overhead due to the creation of new array objects.

Library

None. No external libraries are used in this benchmark.

Special JS feature/syntax

None mentioned in this benchmark. However, note that spread syntax (...) is a relatively recent addition to JavaScript (introduced in ES6) and may not be supported by older browsers or environments.

Other alternatives

In addition to these three methods, other ways to append elements to an array include:

• Using Array.prototype.push.apply()
• Using Array.prototype.splice()
• Using Array.prototype.unshift() followed by Array.prototype.slice()

These alternatives may have varying levels of performance and readability compared to the three methods being tested.

Benchmark preparation code

The benchmark preparation code creates two arrays, one with 10 elements and another with 20 elements, using Array.prototype.fill():

var array = [].fill(0, 10, 100)
var array2 = [].fill(0, 20, 100)

This code prepares the input data for the benchmark tests.

Individual test cases

Each test case measures the execution time of a specific method:

• Push with spread syntax: array.push(...array2)
• Spread syntax: array = [...array, ...array2]
• Concat(): array = array.concat(array2)

These test cases capture the performance differences between each method.