The benchmark provided in the JSON consists of two different approaches to iterating over and processing an array of objects in JavaScript. The focus is on comparing two methodologies for retrieving unique identifiers from a list: using Array.prototype.map and Array.prototype.filter methods versus using a traditional for...of loop.

Test Cases Overview

1. For-Each

   • This approach uses the map function two times, where the first maps to create an array of object identifiers (objectId), and the second filters out undefined values. The process results in the creation of a Set, which inherently provides unique values.
   • Example Code:

     const exampleObjects = Array.from(Array(1000)).map((_, i) => {
       const randomId = Math.round(Math.random() * 100);
       const otherRandomId = Math.round(Math.random() * 100);
       return {
         objectId: i % 3 === 0 ? undefined : randomId.toString(),
         clientObjectId: i % 4 === 0 ? undefined : otherRandomId.toString(),
       };
     });
     const objectIds = new Set(exampleObjects.map(i => i.objectId).filter(i => i !== undefined));
     const clientObjectIds = new Set(exampleObjects.map(i => i.clientObjectId).filter(i => i !== undefined));
     

2. map + filter twice (traditional for loop)

   • This approach is more imperative and involves a single iteration over the array using the for...of loop. It checks each object's properties and adds valid identifiers to the respective Set.
   • Example Code:

     const exampleObjects = Array.from(Array(1000)).map((_, i) => {
       const randomId = Math.round(Math.random() * 100);
       const otherRandomId = Math.round(Math.random() * 100);
       return {
         objectId: i % 3 === 0 ? undefined : randomId.toString(),
         clientObjectId: i % 4 === 0 ? undefined : otherRandomId.toString(),
       };
     });
     
     const objectIds = new Set();
     const clientObjectIds = new Set();
     
     for (const i of exampleObjects) {
       if (i.objectId) objectIds.add(i.objectId);
       if (i.clientObjectId) clientObjectIds.add(i.clientObjectId);
     }
     

Performance Results

The benchmark results indicate the number of executions per second for each method:

• map + filter twice: 20,723 executions per second
• For-Each: 16,738 executions per second

Pros and Cons

1. For-Each (map + filter)

   • Pros:
     • More declarative and concise, leading to potentially higher readability.
     • Makes good use of JavaScript's built-in array methods, which are optimized for performance in many engines.
   • Cons:
     • May involve more overhead due to the creation of intermediate arrays (especially noticeable in larger datasets), as it calls map and filter twice.
     • Each call results in garbage collection of the intermediate objects, which could diminish performance.

2. map + filter (traditional for-loop)

   • Pros:
     • More performant in terms of speed; single traversal of the dataset without creating intermediate arrays.
     • Reduces memory pressure since no additional arrays are generated beyond the final Set.
   • Cons:
     • More verbose; lacks the succinctness of functional programming styles.
     • Might seem less readable at first glance, especially for those less familiar with JavaScript's array manipulation methods.

Other Considerations

• Use Case Appropriateness: Depending on the size and nature of the data, the selection between these methods might change. For small datasets, the impact on performance may not be significant, but with larger datasets, the efficiency of a single pass (as in the traditional for...of) become more advantageous.
• Browser Optimization: JavaScript engines within different browsers can optimize certain patterns more effectively. Continuous benchmarking across environments (like other browsers, or node.js) may yield different results.
• Code Maintainability: While performance is important, maintainability and code clarity should also be taken into consideration. A balance between performance and readability is often ideal in larger codebases.

Alternatives

• Reduce: An alternative could be employing the Array.prototype.reduce method to achieve a similar result in a single traversal, accumulating results directly into the Set.

  const objectIds = exampleObjects.reduce((set, obj) => {
    if (obj.objectId) set.add(obj.objectId);
    return set;
  }, new Set());
  

This benchmark illustrates key differences in approaches to processing data in JavaScript, emphasizing performance while highlighting readability and maintainability.