Let's dive into the world of JavaScript microbenchmarks on MeasureThat.net.

What is being tested?

MeasureThat.net is testing two different approaches for updating an array in JavaScript: using the forEach method and using the map method. The benchmark compares the performance of these two approaches on a large array with 1000 elements.

Options compared

There are two options being compared:

1. Array.forEach: This method updates each element in the array by iterating through it, which can be slow for large arrays.
2. Array.map: This method creates a new array with the updated values without modifying the original array, which is generally faster.

Pros and Cons

• Array.forEach:
  • Pros: Can update each element individually, potentially more efficient for small updates.
  • Cons: Iterates through the entire array, making it slower for large arrays.
• Array.map:
  • Pros: Creates a new array with updated values without modifying the original array, making it faster for large arrays.
  • Cons: Can be memory-intensive if dealing with very large datasets.

Library and purpose

In this benchmark, no specific library is used. The benchmark focuses on native JavaScript methods.

Special JS feature or syntax

There are no special JavaScript features or syntax being tested in this benchmark. However, it's worth noting that the map method uses a more modern, concise syntax, which may be considered a minor optimization by some developers.

Other alternatives

Other approaches for updating an array could include:

• Using a loop with an index variable (e.g., for (var i = 0; i < arr.length; i++) { arr[i].timeMs = 1 })
• Using the reduce method to update each element individually
• Using a library like Lodash or Underscore.js, which provides utility functions for array operations

Keep in mind that these alternatives may have different performance characteristics compared to the forEach and map methods.

Benchmark preparation code

The benchmark preparation code is minimal, as it only initializes an array of 1000 elements using Array.from. The forEach and map tests then update this array by setting a specific property (timeMs) to 1.