Benchmark Overview

The benchmark titled "Map copying" is designed to evaluate different methods of copying a Map object in JavaScript. The benchmark executes three distinct approaches to creating a new Map initialized with the entries of an existing one.

Test Cases Overview

1. From map:

   • Definition: return new Map(map);
   • Description: This approach directly uses the Map constructor, which accepts an existing Map instance to create a new copy of it.

2. From array:

   • Definition: return new Map([...map])
   • Description: This method spreads the existing Map into an array using the spread operator (...) and then passes that array to the Map constructor to create a new Map.

3. Step-by-step:

   • Definition:

     const newMap = new Map();
     map.keys().forEach(x => newMap.set(x, map.get(x)));
     return newMap;
     

   • Description: This method manually iterates over each key in the original Map, retrieves the corresponding value, and sets it in a new Map one-by-one.

Performance Results

The benchmark measures the performance by computing the number of executions per second for each method. The results are as follows:

• From map:

  • Executions per second: 1513.997
  • This method is the fastest, indicating it's the most efficient way to copy a Map.

• Step-by-step:

  • Executions per second: 1241.901
  • This is slower than the From map approach, likely due to the overhead of repeatedly accessing the original Map and inserting entries individually.

• From array:

  • Executions per second: 1112.976
  • This is the slowest method among the three, as the spreading process into an array introduces additional overhead.

Pros and Cons of Each Approach

1. From map (Direct Constructor):

   • Pros:
     • Fastest execution time as observed in the benchmark.
     • Straightforward and clear in intention, directly replicates the Map.
   • Cons:
     • None significant; it's optimal for standard duplication.

2. From array (Spread Operator):

   • Pros:
     • Utilizes modern syntax and is readable.
     • Can be more flexible for altering or filtering items before adding.
   • Cons:
     • Performance is less optimal compared to directly using the Map constructor with an existing Map.
     • Spreading can be less efficient due to intermediate step of creating an array.

3. Step-by-step (Iterative Approach):

   • Pros:
     • Clear and understandable for beginners, especially those familiar with basic iteration.
     • May allow for customization, such as transforming keys/values while copying.
   • Cons:
     • Least efficient in terms of performance, due to the iterative nature of the method.
     • Additional overhead from multiple method calls (get and set).

Other Considerations

• Use Cases: The choice of method can depend on how the Map is used in the application. If performance is critical and frequent copying is required, the From map method is recommended.
• Readability vs. Performance: It's essential to find a balance. While direct constructor usage (From map) is optimal, readability might favor the other methods in contexts where performance is not a bottleneck.
• Alternatives: Other alternatives for duplicating maps may include converting to Object and back to Map, but that could result in data structure transformation losses and is often less efficient.

These performance insights can help developers choose the most suitable method for copying Map instances depending on their specific application's requirements and performance needs.