Benchmark Overview

The benchmark titled "Merge+object.keys vs set vs for" evaluates three different methods for merging the keys from two JavaScript objects (a and b), specifically looking at how efficiently they can consolidate the unique keys. The benchmark compares the following approaches:

1. Set: Using the Set object combined with the spread operator to collect keys.
2. Merge: Using the object spread syntax to merge the objects directly and then retrieve the keys.
3. For: Utilizing traditional for...in loops to iterate over the objects and gather unique keys into a Set.

Test Approaches

1. Set:

   • Definition:

     const s = new Set([...Object.keys(a), ...Object.keys(b)]);
     const res = Array.from(s);
     

   • Pros:
     • Automatically handles duplicate keys due to the nature of Set, ensuring that each key is unique.
     • The spread operator (...) provides a concise way to combine arrays.
   • Cons:
     • May have a performance overhead due to the creation of an intermediate array and then converting it back to an array with Array.from.
   • Considerations: The performance can vary broadly depending on object size but is generally effective for merging unique keys.

2. Merge:

   • Definition:

     const c = { ...a, ...b };
     const res = Object.keys(c);
     

   • Pros:
     • Simplicity and readability. The object spread syntax is very clear and easy to understand, merging objects seamlessly.
     • The final call to Object.keys produces a straightforward array of keys representing the merged object.
   • Cons:
     • If a and b have large numbers of keys, this can lead to more memory usage since a new object is created.
   • Considerations: This syntax is well-optimized in modern JavaScript engines, making it typically very efficient.

3. For:

   • Definition:

     const s = new Set();
     for (const x in a) s.add(x);
     for (const x in b) s.add(x);
     const res = Array.from(s);
     

   • Pros:
     • Works well for environments that do not support the spread operator or object spread syntax, providing a backward-compatible solution.
     • No intermediate array is created directly in the merging process.
   • Cons:
     • Slightly more verbose and less readable than the other methods.
     • The use of for...in can inadvertently include properties from the prototype chain unless safeguards are put in place (like checking hasOwnProperty).
   • Considerations: The performance could vary based on how many properties are added and whether prototype properties are involved.

Benchmark Results

The benchmarking showed the following performance results (executions per second):

• Merge: 1,730,753.875
• For: 1,196,404.5
• Set: 761,872.0625

Summary of Findings

• The Merge approach performed the best, indicating that the modern object spread syntax has been optimized in contemporary JavaScript engines for merging objects.
• The For loops were slower but still performed quite well, showcasing their reliability across different environments.
• The Set method, while clear and efficient in terms of deduplication, showed the slowest execution speed, likely influenced by the overhead of creating both a temporary array and the Set.

Alternatives

Other alternatives to the methods evaluated can include:

• Using Array.prototype.filter combined with concat to filter out the unique keys which can be slower than the object spread:

  const res = [...Object.keys(a).concat(Object.keys(b))]
    .filter((value, index, self) => self.indexOf(value) === index);
  

• Using external libraries like Lodash, which provides utility functions like _.uniq and _.merge:

  const res = _.uniq([...Object.keys(a), ...Object.keys(b)]);
  

• Immutable.js: An additional option if working with a functional programming mindset that emphasizes immutability and persistent data structures.

These alternatives may offer different trade-offs in terms of readability, performance, and memory usage depending on the specific context of their implementation.