Let's dive into the world of JavaScript microbenchmarks!

Benchmark Overview

The provided benchmark measures the performance of different methods to create an array in JavaScript: Array.apply, Array.from, map, and two looping approaches (Loop and assign and Loop and push). The goal is to determine which method is the fastest.

Method Comparison

Here's a brief overview of each method:

1. Array.apply(null, new Array(10)).map(() => false): This method uses Array.apply to create an array with 10 elements, then maps over it to return false. The resulting array is not used; it's only iterated over.
2. Array.from({ length: 10 }, () => false): This method creates a new array using the Array.from() constructor, which takes an iterable as an argument and returns a new array with the same elements. In this case, it creates an array of 10 falsy values.
3. new Array(10).map(() => false): Similar to the first method, but uses new Array() to create an empty array, then maps over it to return false.
4. const r = []; for (let i = 0; i < 10; i++) r[i] = false;: This is a looping approach that creates an array by iterating over a range of indices and assigning values to the array elements.
5. const r = []; for (let i = 0; i < 10; i++) r.push(false);: Another looping approach, but uses push() to add elements to the end of the array.

Pros and Cons

Here's a brief summary of each method:

1. Array.apply: Fast, as it avoids creating an intermediate array. However, it requires null to be used as the first argument.
2. Array.from: Creates a new array with a specified length, which can be beneficial for performance. However, it's not supported in older browsers and may incur a slight overhead due to the constructor call.
3. map: Similar to apply, but creates an intermediate array that needs to be iterated over.
4. Looping approaches:
   • Loop and assign: Slow, as it involves iterating over indices and assigning values to elements. However, it's a simple and widely supported approach.
   • Loop and push: Similar to the first looping approach, but uses push() instead of indexing.

Library Usage

There is no explicit library usage in this benchmark. However, Array.from() relies on the Array constructor and some browser-specific features (e.g., length property).

Special JS Features or Syntax

None are explicitly used in this benchmark.

Other Considerations

• Browser support: The benchmark uses a modern Chrome version, which is not representative of older browsers. If you want to test cross-browser compatibility, you may need to use different implementations.
• Execution count: The benchmark measures the number of executions per second (ExecutionsPerSecond), which can be affected by various factors, such as system load, memory constraints, and interpreter optimization.

Alternatives

If you're looking for alternatives or variations on these methods, consider:

1. Using Array.prototype.slice() instead of map.
2. Creating arrays using other methods, like Array.prototype.concat(), Array.prototype.push(), or Set constructors.
3. Experimenting with different iteration patterns, such as using a for...of loop or reduce().