Let's break down the provided benchmark and explain what's being tested.

Benchmark Overview

The benchmark is designed to compare two approaches: class instance method lookup and function-created object method lookup.

Class Instance Method Lookup

In this approach, an instance of the AClass class is created and its b() method is invoked directly on the instance. The b() method returns a value, which is then executed and measured by the benchmark.

This approach tests how JavaScript engines execute methods on objects that are instances of classes. It's essential to note that this type of lookup is commonly used in object-oriented programming (OOP) scenarios.

Function-Created Object Method Lookup

In this approach, an object is created using a function expression (window.AFunc = function() {...}), and its b() method is invoked directly on the object. The b() method also returns a value, which is then executed and measured by the benchmark.

This approach tests how JavaScript engines execute methods on objects that are not instances of classes but rather objects created using function expressions.

Pros and Cons

Both approaches have their pros and cons:

• Class instance method lookup:
  • Pros: This approach is commonly used in OOP scenarios, and it's easy to understand the intent of the code.
  • Cons: It may lead to slower execution times due to the need for additional overhead to find the correct method on the object.
• Function-created object method lookup:
  • Pros: This approach can be faster since there's no need for additional overhead to find the correct method on the object. Additionally, it allows for more flexibility in creating objects with specific properties and methods.
  • Cons: It may lead to confusion when reading code, especially if the function expression is complex.

Library

There doesn't appear to be any external library used in this benchmark.

Special JS Features or Syntax

There are no special JavaScript features or syntaxes being tested in this benchmark. The focus is on understanding how different approaches affect performance.

Other Alternatives

To create a similar benchmark, you could consider the following alternatives:

• Using prototypes and this keyword to test method invocation on objects.
• Creating an object using constructors (e.g., new AFunc()).
• Comparing the performance of function expressions versus constructor functions for creating objects.

Keep in mind that these alternatives might require adjustments to the benchmark's setup and script preparation code.