I'd be happy to help you understand the JavaScript microbenchmark on MeasureThat.net.

Benchmark Overview

The benchmark compares two approaches for performing a union operation: Lodash's _.union() function and native JavaScript's Set constructor.

Script Preparation Code

The script preparation code sets up two arrays, a and b, which contain elements to be used in the union operation. The arrays are:

var a = [1, 2, 3, 4, 5]
var b = [3, 4, 5, 6, 7]

Html Preparation Code

The HTML preparation code includes a script tag that loads Lodash version 4.17.5 from a CDN.

<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.min.js'></script>

Benchmark Definition

The benchmark definition specifies two test cases:

1. _.union: This test case uses Lodash's _.union() function to perform the union operation.
2. Set(): This test case uses native JavaScript's Set constructor to perform the union operation.

Comparison of Approaches

Let's compare the two approaches:

Lodash's _.union():

Pros:

• Well-documented and widely used library
• Optimized for performance (especially when dealing with large datasets)
• Supports various data types, including arrays, numbers, and strings

Cons:

• Adds additional overhead due to library imports
• May have slower startup times compared to native implementations

Native JavaScript's Set:

Pros:

• Native implementation means faster execution speeds
• No additional overhead or dependencies
• Fast and efficient for large datasets

Cons:

• Requires manual handling of iterations (e.g., using for...of loops)
• Limited support for various data types, especially complex ones

Library: Lodash

Lodash is a popular JavaScript utility library developed by Isaac Schlueter. It provides a wide range of functional programming tools and helpers for tasks such as array manipulation, object transformation, and more.

In this benchmark, Lodash's _.union() function is used to perform the union operation. The implementation is likely optimized for performance, which explains its relatively fast execution speeds in the benchmark.

Special JS Feature or Syntax

This benchmark does not utilize any special JavaScript features or syntax beyond standard ES6/ES7 features, such as template literals, arrow functions, and for...of loops. If it did, I'd be happy to explain them further!

Other Alternatives

If you're looking for alternatives to Lodash's _.union() function or native JavaScript's Set constructor, here are a few options:

• For union operations:
  • Microsoft's Array.prototype.union(): A polyfilled implementation of the union() method that can be used with arrays.
  • Immutable.js: A library for working with immutable data structures, which includes methods for performing unions.
• For native JavaScript's Set constructor:
  • Google's Array.prototype.sort() and Array.prototype.unique(): These methods can be used to create a set-like behavior for arrays.

I hope this explanation helps you understand the JavaScript microbenchmark on MeasureThat.net!