Let's dive into the world of JavaScript microbenchmarks and explore what's being tested on MeasureThat.net.

What is being tested?

The provided benchmark is comparing two ways to create an array in JavaScript:

1. Using Array.from(): This method creates a new array by iterating over an iterable object (in this case, an empty object with a length of 10) and mapping each iteration to produce a value.
2. Creating an array using the new Array() constructor with three arguments: length, fillValue, and startIndex. In this case, length is set to 10, fillValue is set to 0, and startIndex is set to 0.

Options compared

The two approaches are being compared in terms of their performance. Specifically, the benchmark measures how many executions per second (ExecutionsPerSecond) each approach can handle on a given machine.

Pros and cons of each approach:

• Array.from(): This method has several advantages:
  • It's more concise and readable.
  • It's more memory-efficient, as it only creates an array of the required length.
  • It's more flexible, as you can pass any iterable object to it. However, it also has some disadvantages:
  • It may have a higher overhead due to the creation of an intermediate iterator object.
  • It may not be optimized for performance in all browsers or environments.
• new Array(length): This method is often preferred when you need more control over the array's properties:
  • You can specify the fill value and start index explicitly.
  • You can create arrays with a specific length, which can be useful for caching or other optimization techniques. However, it also has some disadvantages:
  • It's less concise and may require more code to achieve the same result as Array.from().
  • It creates an array of the required length immediately, which may consume more memory.

Other considerations:

• Browser support: Both methods are widely supported by modern browsers. However, the performance differences between them might be more pronounced in older browsers or environments.
• Memory usage: The new Array method is generally less memory-efficient than the Array.from() method, especially for large arrays.

Library and special features

There doesn't seem to be any libraries being used in this benchmark, nor are there any special JavaScript features or syntax being tested. The focus is purely on comparing two different approaches to creating an array in JavaScript.

Other alternatives:

If you're looking for alternative methods to create an array in JavaScript, some options include:

• Using the spread operator ([...]) to create a new array:

const arr = [...new Array(10)];

• Using Array() with two arguments (length and init):

const arr = new Array(10, 0);

However, these alternatives may not be as performant or memory-efficient as the methods being compared in this benchmark.

I hope this explanation helps you understand what's going on in this JavaScript microbenchmark!