Benchmark Overview

MeasureThat.net is a website that allows users to create and run JavaScript microbenchmarks, comparing different approaches for common use cases. The provided JSON represents the benchmark definition, which includes three test cases: creating an empty array using Array.from(), new Array().fill(undefined), and the spread operator [... new Array(1000)].

Test Case Breakdown

1. Array.from({ length: 1000 });: This test case creates a new array with 1000 elements, all initialized to undefined. The Array.from() method is used to create an array from an iterable object (in this case, an empty object with a length property).
2. new Array( 1000 ).fill( undefined );: This test case creates a new array with 1000 elements, all initialized to undefined. The new Array() constructor is used to create a new array, and the .fill() method is used to fill it with the specified value.
3. [... new Array(1000)]: This test case uses the spread operator to create a new array from an existing one. The [... ] syntax creates a new array by spreading the elements of new Array(1000), which are all initialized to undefined.

Comparison and Pros/Cons

The three approaches have different characteristics:

• Array.from(): This method is more concise and readable, but it may incur additional overhead due to the need to create an iterable object. On the other hand, it's a modern JavaScript feature that's widely supported.
• new Array().fill(undefined): This approach is straightforward and efficient, as it uses the new Array() constructor and the .fill() method directly. However, it may not be as concise or readable as Array.from().
• Spread operator [... new Array(1000)]: This approach is concise and easy to read, but it may incur additional overhead due to the need to create a new array.

Pros and cons of each approach:

• Array.from():
  • Pros: Concise, readable, modern JavaScript feature.
  • Cons: May incur additional overhead.
• new Array().fill(undefined):
  • Pros: Efficient, straightforward, widely supported.
  • Cons: Less concise, less readable than Array.from().
• Spread operator [... new Array(1000)]:
  • Pros: Concise, easy to read.
  • Cons: May incur additional overhead.

Library and Special Features

There are no libraries mentioned in the provided JSON. However, it's worth noting that JavaScript has a few special features that might be used in microbenchmarks:

• Async/await: Not present in this benchmark, but it could be used to measure performance of asynchronous code.
• Generators: Not present in this benchmark, but they could be used to measure performance of iterative algorithms.

Other Alternatives

If you're looking for alternative ways to create an empty array, here are a few options:

• Using the Array() constructor with no arguments: new Array()
• Using a loop to create an empty array: [] = [];

Keep in mind that these approaches may not be as efficient or concise as the ones mentioned earlier.