The benchmark on MeasureThat.net titled "Set union methods even more with builtin" evaluates different methods for combining two JavaScript Sets. Sets are a built-in JavaScript object that allows the storage of unique values, making them useful for operations like unions. The benchmark presents various ways to achieve the union of two sets (set1 and set2), which have been initialized with specific values in the preparation code.

Test Cases and Their Descriptions:

1. Spreading

   • Definition: const set3 = new Set([...set1, ...set2]);
   • Description: This method uses the spread operator (...) to expand the elements of both sets into a new Set.
   • Pros: Concise and easy to understand.
   • Cons: Performance can be affected by the size of the sets since it creates temporary arrays.

2. Set.forEach + Set.add

   • Definition: const set3 = new Set(set1); set2.forEach(el => set3.add(el));
   • Description: A new Set is initialized from set1, and then elements from set2 are added one by one using forEach.
   • Pros: Slightly more flexible compared to the spread operator, particularly if you want to manipulate elements during addition.
   • Cons: May be less concise and slightly slower due to the explicit loop.

3. Generators

   • Definition: const set3 = new Set(function*() { yield* set1; yield* set2; }());
   • Description: This method utilizes a generator function to yield values from both sets to create a new Set.
   • Pros: Can be powerful if you are combining more complex data sources; lazy evaluation might be beneficial in some scenarios.
   • Cons: Potentially less intuitive for new developers, and may introduce overhead associated with the generator.

4. for loop

   • Definition: const set3 = new Set(set1); for(let el of set2) set3.add(el)
   • Description: A traditional for...of loop is used to iterate through set2 and add elements to a new Set initialized with set1.
   • Pros: Clear intention and familiarity among developers who are used to loops.
   • Cons: Slightly more verbose than other methods, especially if there's no need to manipulate elements.

5. builtin union

   • Definition: console.log(set1.union(set2).size)
   • Description: This benchmark refers to a hypothetical built-in method for union, which does not exist in JavaScript's standard Set implementation.
   • Pros: If it existed, it would be the most concise and likely the most optimized way of performing union operations.
   • Cons: Since it's not part of the current JavaScript specification, it cannot be used directly with the standard Set object.

Benchmark Results:

The results show the performance (in executions per second) of each method as tested under a specific environment (Chrome 134 on macOS). The Set.forEach + Set.add method was the fastest, followed closely by the spread operator. The built-in union method, although hypothetical, performed well among the available tests, while the generator method was the slowest.

Alternatives:

As with any programming task, alternatives also exist:

• Using Arrays: If duplicates are not a concern, using arrays to store the union, followed by a filtering step to ensure uniqueness, is a straightforward method.
• Libraries: Utility libraries such as Lodash have methods for union operations which can encapsulate best practices and optimizations.
• Custom Implementations: Developers may also implement their union logic, leveraging the unique characteristics of their datasets.

Each of these approaches has its trade-offs in terms of complexity, readability, performance, and compatibility. When choosing a method for union operations, developers should consider the size of their data, the importance of code clarity, and whether performance is a critical factor in their specific context.