Let's dive into the world of JavaScript microbenchmarks!

What is being tested?

The provided benchmark compares the performance of two approaches to create a new object by spreading an existing object and adding new properties: using the spread operator (...) and using Object.assign(). The test case focuses on creating a single addition operation, which means only one property is added to the original object.

Options compared

Two options are being tested:

1. Using the spread operator: This approach uses the syntax { ...obj, ...single } to create a new object that inherits properties from obj and adds the single property.
2. Using Object.assign(): This approach uses the method Object.assign(obj, { single: 'foo' }) to merge two objects: the original object obj and an object with the single property.

Pros and Cons

• Using the spread operator:
  • Pros:
    • More concise and readable code.
    • Efficient in terms of performance, as it only creates a new object reference.
  • Cons:
    • May be less intuitive for developers who are not familiar with this syntax.
• Using Object.assign():
  • Pros:
    • Widely supported and well-established method.
    • May be more readable for some developers due to its explicit nature.
  • Cons:
    • Creates a new object reference, which can lead to unnecessary memory allocation.

Library: Object.assign()

Object.assign() is a built-in JavaScript method that returns a new object with the properties of all the specified source objects. It is used extensively in modern JavaScript development and is supported by most browsers and Node.js versions.

Special JS feature/syntax: None mentioned

This benchmark does not use any special JavaScript features or syntax beyond what's commonly known.

Other alternatives

While Object.assign() has been widely adopted, there are other methods that can achieve similar results:

• Spread operator with array: const finalObj = { ...obj, ...['single'] }. Note that this creates an array, which may lead to unexpected behavior if not handled correctly.
• Array spread and Object.fromEntries(): const finalObj = Object.fromEntries([[...obj, single: 'foo']]. This approach is more explicit but has similar performance characteristics to Object.assign().

In summary, the benchmark compares two approaches to create a new object by spreading an existing object and adding a new property. The spread operator offers concise code with good performance, while Object.assign() provides a well-established method with slightly less efficient overhead.