The benchmark named "Array splice vs array assign" compares two methods of updating an object within an array in JavaScript: using the splice method and using direct assignment of an object property.

Benchmark Tests

1. Array splice:

   const index = input.findIndex(val => val.id === 999);
   input.splice(index, 1, {id: 999, data: 'somethingElse'});
   

   • Description: This test first locates the index of the object with id 999 using findIndex. It then removes that object and inserts a new object at the same index using splice.
   • Pros:
     • splice can directly modify the original array and is useful for operations where you need to both remove and add an element simultaneously.
     • It can be more readable when performing multiple operations in one step.
   • Cons:
     • Involves more operations (removal and addition), which can be slower in larger arrays.
     • Potential performance overhead due to managing array length and re-indexing.

2. Object property assign:

   const index = input.findIndex(val => val.id === 999);
   input[index] = {id: 999, data: 'somethingElse'};
   

   • Description: This test also finds the index of the object with id 999, but it replaces the object at that index directly with a new object.
   • Pros:
     • Simpler and potentially faster than splice for simply replacing an object, as it only requires accessing the index and changing the value.
     • Avoids the overhead of modifying the array structure.
   • Cons:
     • It does not allow for removal of an object in the same operation, which can be a limitation in some scenarios (though unnecessary for this benchmark).

Performance Results

• The test results indicate that the "Object property assign" method has a higher execution rate (1,420,837 executions per second) compared to "Array splice" (1,379,187 executions per second). This suggests that direct property assignment is generally more performant than splicing in this context.

Other Considerations

• Memory Management: When using splice, the underlying implementation might create intermediate arrays or deal with re-allocation, which can be less memory efficient. Direct assignment only replaces a reference, leading to a smaller memory overhead.
• Readability and Maintainability: Sometimes, maintainability and readability can be as critical as performance, depending on the size and complexity of your application. The choice between these methods can depend on developer preference and specific application requirements.

Alternatives

• Using map: If bulk updates across an array are needed, using map can be a more functional approach:

  input = input.map(val => val.id === 999 ? {id: 999, data: 'somethingElse'} : val);
  

  • This creates a new array with updated values without modifying the existing array, and it can be more declarative.

• Using Libraries: Libraries like lodash or Immutable.js can manage state updates more efficiently. For instance, Immutable.js helps in maintaining immutability which leads to reliable performance in larger applications.

In summary, the benchmark evaluates two different approaches to updating an array of objects, with performance metrics clearly favoring direct assignment over splice. Each method has its use cases and can be chosen based on specific requirements at hand.