Let's break down what's being tested in this benchmark.

What is being tested?

The benchmark is testing two approaches to create a new object by merging two existing objects: the spread operator (...) and Object.assign().

Options compared:

1. Spread Operator (...):
   • The spread operator is a syntax introduced in ECMAScript 2018 (ES2018) that allows you to extract properties from an object and merge them into a new object.
   • This approach creates a shallow copy of the original objects, meaning that nested objects are not merged recursively.
   • The syntax is simple and concise: const obj3 = { ...obj1, ...obj2 };
2. Object.assign():
   • Object.assign() is a method that returns a new object with the properties from the specified source objects.
   • This approach also creates a shallow copy of the original objects.
   • The syntax is more verbose: const obj3 = Object.assign({}, obj1, obj2);

Pros and Cons:

• Spread Operator (...):
  • Pros:
    • More concise syntax
    • Easier to read and write
  • Cons:
    • May not be supported in older browsers or environments (not tested in this benchmark)
    • Creates a shallow copy, which might lead to unexpected behavior if working with nested objects
• Object.assign():
  • Pros:
    • Widely supported across browsers and environments
    • Can create a deep copy of objects if the proto property is preserved (not tested in this benchmark)
  • Cons:
    • More verbose syntax
    • May not be as concise or readable

Library usage:

None, as both approaches are native JavaScript syntax.

Special JS feature/syntax:

• The spread operator (...) uses the rest parameter syntax, which was introduced in ECMAScript 2015 (ES6).
• Object.assign() is a standard method defined by the ECMAScript specification.

Other considerations:

Both approaches have their own use cases and performance characteristics. In general, the spread operator is preferred for its concise syntax, while Object.assign() is often used when working with older browsers or environments that don't support the spread operator.

Alternatives:

For creating a new object by merging two existing objects, you can also consider other approaches:

1. Using Object.create() and Object.prototype.hasOwnProperty: This method involves creating a new object using Object.create() and then adding properties to it using the hasOwnProperty() method.
2. Using a library like Lodash's mergeDeep() function: If you need more control over the merging process, libraries like Lodash provide functions that can help you achieve this.

Keep in mind that these alternatives might have their own trade-offs in terms of performance, readability, and support across browsers and environments.