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

What's being tested?

The benchmark is comparing the performance of two approaches to merge two objects: using the JavaScript spread operator (...) and using Object.assign() without mutating the original object.

Options compared

The two options being compared are:

1. Using the JavaScript spread operator: This approach uses the ... syntax to create a new object that includes all properties from both firstObject and secondObject.
2. Using Object.assign() without mutation: This approach creates a new object by calling Object.assign() with an empty object as the target, and then merging the properties of firstObject and secondObject into it.

Pros and cons

• Using the JavaScript spread operator:
  • Pros:
    • More concise and expressive syntax
    • Less error-prone than using Object.assign()
  • Cons:
    • Can be slower due to object creation overhead
    • May not be compatible with older browsers or environments that don't support the spread operator
• Using Object.assign() without mutation:
  • Pros:
    • Faster and more efficient, as it avoids object creation overhead
    • More widely supported across different browsers and environments
  • Cons:
    • Less concise and expressive syntax
    • May be more prone to errors if not used correctly

Library/Dependency

Neither of these approaches relies on a specific library or dependency. However, Object.assign() is a built-in method in JavaScript that has been available since ECMAScript 2015 (ES6).

Special JS feature/syntax

There are no special JS features or syntax being tested in this benchmark.

Other alternatives

If you want to explore other approaches to merging objects, here are some alternatives:

1. Using the Object.keys() and reduce() methods: You can use Object.keys() to get an array of property names from both objects, and then use reduce() to create a new object with merged properties.
2. Using a library like Lodash: If you need more complex merging logic or want to take advantage of additional features like memoization, you can consider using a library like Lodash.

Here's an example implementation using the Object.keys() and reduce() methods:

const firstObject = { sampleData: 'Hello world' };
const secondObject = { moreData: 'foo bar' };

const finalObject = Object.keys(firstObject).reduce((obj, key) => {
  obj[key] = firstObject[key];
}, {});
finalObject[Object.keys(secondObject)[0]] = secondObject[Object.keys(secondObject)[0]];

And here's an example implementation using Lodash:

import _ from 'lodash';

const firstObject = { sampleData: 'Hello world' };
const secondObject = { moreData: 'foo bar' };

const finalObject = _.merge({}, firstObject, secondObject);

Note that these alternatives may have different performance characteristics or trade-offs depending on your specific use case.