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

What is being tested?

The benchmark measures the performance of two approaches to create a deep copy of an object:

1. Lodash cloneDeep: This method uses the cloneDeep function from the Lodash library, which recursively clones the entire object.
2. Object.assign: This method creates a new object and copies the properties from the original object into it.

Options compared

The two options being compared are:

• Recursion vs Iteration: Lodash cloneDeep uses recursion to create a deep copy of the object, while Object.assign iterates over the properties of the original object to create a new one.
• Library usage: Lodash cloneDeep relies on the Lodash library for its implementation, whereas Object.assign is a native JavaScript function.

Pros and Cons

• Lodash cloneDeep: Pros:
  • Easy to implement and use
  • Handles nested objects and arrays correctly
  • Supports many other functions from Lodash
• Cons:
  • Additional overhead due to the need for the Lodash library
  • Might be slower than Object.assign due to the extra function call
• Object.assign: Pros:
  • Fastest way to create a shallow copy of an object
  • Native JavaScript function, no additional overhead
• Cons:
  • Only creates a shallow copy (first-level only)
  • May not handle nested objects and arrays correctly

Library usage

The Lodash library is used for the cloneDeep function. It provides a convenient way to create deep copies of objects, as well as many other utility functions.

Special JavaScript feature or syntax

There is no specific special JavaScript feature or syntax being tested in this benchmark. Both approaches are standard JavaScript methods.

Other alternatives

If you need to create a deep copy of an object without using Lodash, you can implement your own recursive function:

function cloneDeep(obj) {
  if (typeof obj !== 'object' || obj === null) return obj;

  const clone = Array.isArray(obj) ? [] : {};

  for (const key in obj) {
    clone[key] = cloneDeep(obj[key]);
  }

  return clone;
}

Alternatively, you can use a library like lodash or json-stringify-safe to create deep copies of objects.

Benchmark preparation code

The script preparation code defines two objects:

• MyObject: The original object with nested properties
• myCopy: The variable that will store the cloned copy of MyObject

The Html Preparation Code includes external scripts for Lodash and Object-assign-polyfill, as they are required for this benchmark.

Individual test cases

There are two test cases:

1. Lodash cloneDeep: Creates a deep copy of MyObject using the cloneDeep function from Lodash.
2. Json clone: Creates a shallow copy of MyObject using the Object.assign method.

These test cases measure the performance of each approach under different conditions, including various browsers and devices.