The provided benchmark tests the performance of two methods for deep equality checking on JavaScript objects—_.isEqual from the Lodash library and using JSON.stringify. The benchmark is divided into three levels, corresponding to the complexity and nesting of the objects being compared.

Benchmark Breakdown

1. Comparison Options:

• _.isEqual: This is a utility function from Lodash that performs a deep comparison between two values to determine if they are equivalent. It can handle nested objects and accounts for various data types effectively.
• JSON.stringify: This method converts a JavaScript object into a JSON string, which can then be compared using a strict equality check (===). However, this method is limited as it will not handle certain types of data, such as functions, undefined, and cyclic objects.

2. Test Cases: The benchmark includes six test cases, organized into three levels of object depth:

• Level 1:
  • _.isEqual(window.foo1, window.bar1)
  • JSON.stringify(window.foo1) === JSON.stringify(window.bar1)
• Level 2:
  • _.isEqual(window.foo2, window.bar2)
  • JSON.stringify(window.foo2) === JSON.stringify(window.bar2)
• Level 3:
  • _.isEqual(window.foo3, window.bar3)
  • JSON.stringify(window.foo3) === JSON.stringify(window.bar3)

Pros and Cons of Each Approach:

_.isEqual:

• Pros:
  • Handles nested objects and arrays robustly.
  • Considers different data types (e.g., dates, numbers, strings) and their specific equality rules.
  • Can work with non-serializable properties (like functions).
• Cons:
  • May be slower in performance as it inspects each property recursively and handles different cases regarding data types.

JSON.stringify:

• Pros:
  • Simple and straightforward implementation.
  • Efficient for flat objects or objects without any complex data types.
• Cons:
  • Does not handle non-serializable values (functions, undefined, symbols).
  • May produce differing results for objects with same structure but in different orders (as it does not account for key order in JSON).
  • Cannot handle cyclic references, which can lead to errors.

Other Considerations:

• The benchmark preparation defines three sets of objects (foo1, bar1; foo2, bar2; foo3, bar3) with subtle differences designed to test the efficacy of the two methods across varying nesting levels.
• Results from the benchmark show the number of executions per second for each type of comparison, providing a clear benchmark against which to assess performance.

Alternatives:

Beyond Lodash’s _.isEqual and JSON.stringify for deep equality checks, other methods may include:

• Manual Recursion: A custom utility function that handles deep comparison can be written based on specific needs, which can be optimized for known data shapes, but this requires more development time.
• Libraries: Other libraries like Ramda have their own implementations (e.g., R.equals) that might differ in performance and capabilities.
• Native Web APIs: In Node.js environments, libraries like fast-deep-equal provide very performant deep equality checks often optimized for speed.

In summary, this benchmark provides clear insights into the performance of two popular methods for checking deep equality in JavaScript objects, considering various aspects including performance and ability to handle complex data structures.