In this benchmark, the performance of two different JavaScript approaches for processing an array is being tested: using the forEach method and the map method. Both approaches are commonly used for iterating over arrays in JavaScript, but they offer different functionalities and have distinct pros and cons.

Benchmark Overview

1. Purpose: The benchmark compares the performance of Array.prototype.forEach() and Array.prototype.map() when generating an array from an existing array.

2. Setup: An array of 100 elements is created using var array = new Array(100);, which serves as the base input for both operations.

Test Cases

1. ForEach:

   • Code:

     const result = [];
     array.forEach(function(i) {
       result.push(i);
     });
     

   • Test Name: forEach
   • Behavior: The forEach method executes a provided function once for each array element, facilitating an operation that pushes each item into a new result array.
   • Pros:
     • Straightforward for side-effects (executing a function for its side effects, such as pushing to an external array).
     • Easier for looping through an array when the result isn't used to create a new array.
   • Cons:
     • Does not return a new array, which might result in additional steps to gather results from it.
     • It’s generally not chainable like other array methods.

2. Map:

   • Code:

     const result = array.map(function(i) {
       return array[i];
     });
     

   • Test Name: map
   • Behavior: The map method creates a new array populated with the results of calling a provided function on every element in the calling array.
   • Pros:
     • Returns a new array directly, containing the results of applying the function to each element.
     • Can help create functional programming patterns and allows method chaining.
   • Cons:
     • Generally used for transforming data rather than for side-effects.
     • If not used for actual transformation (in this case, it redundantly returns the same element), it may be less efficient.

Benchmark Results

In the test results provided, we see the execution speeds of both methods on a specific platform and browser (Firefox 136 on Mac OS X 10.15):

• forEach: 11,177,246 executions per second.
• map: 9,339,928 executions per second.

Conclusion and Considerations

• Performance: The forEach method performed significantly better than the map method in this benchmark scenario. This is partially due to the fact that map does additional work by returning a new array, which may be unnecessary for this case, where the function doesn't change the value being pushed.

• Recommendation: When the goal is simply to iterate through an array for side effects, such as populating a new array or accumulating results, forEach is the preferred choice. When the aim is to transform an existing array into a new one, map is the appropriate method.

Alternatives

1. For Loop: A traditional for loop may provide more granular control and potentially better performance in critical sections, although it sacrifices readability.

   const result = [];
   for (let i = 0; i < array.length; i++) {
       result.push(array[i]);
   }
   

2. Reduce: For complex transformations or when accumulating values, the reduce method is powerful, allowing for constructs that can combine both mapping and reducing in one operation.

   const result = array.reduce((acc, i) => {
       acc.push(i);
       return acc;
   }, []);
   

In conclusion, the choice between forEach, map, and other methods depends on the specific needs of the task (e.g., performance, readability, and functionality). Each method serves different purposes and has its situational strengths.