Let's dive into the benchmark and explain what's being tested.

Benchmark Overview

The MeasureThat.net benchmark compares the performance of two ways to merge objects in JavaScript: using the spread operator (...) and Object.assign(). The benchmark is designed to measure which approach is faster, but it also provides information about the underlying browser, device platform, operating system, and execution frequency.

Benchmark Definitions

The benchmark definition consists of two test cases:

1. Using the spread operator: This test case uses the spread operator (...) to merge two objects: firstObject and secondObject. The resulting merged object is stored in the finalObject.

const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = {
  ...firstObject,
  ...secondObject
}

2. Using Object.assign(): This test case uses the Object.assign() method to merge two objects: firstObject and secondObject. The resulting merged object is stored in the finalObject.

const firstObject = { sampleData: 'Hello world' }
const secondObject = { moreData: 'foo bar' }
const finalObject = Object.assign({}, firstObject, secondObject)

Comparison of Options

The benchmark compares the performance of two approaches:

• Using the spread operator: This approach is a relatively modern feature in JavaScript that was introduced in ECMAScript 2018 (ES8). It uses the rest and spread syntax (...) to create a new object with the properties from firstObject and secondObject.
• Using Object.assign(): This approach has been part of the JavaScript language since ECMAScript 2009 (ES5) and is widely supported by most browsers. It takes an initial value (in this case, an empty object {}) and merges the properties from two or more sources.

Pros and Cons

Here are some pros and cons of each approach:

• Using the spread operator:
  • Pros: More concise and expressive way to merge objects, modern feature that's widely adopted.
  • Cons: May not work in older browsers or environments that don't support ES8.
• Using Object.assign():
  • Pros: Widely supported by most browsers, works in older environments.
  • Cons: Less concise and less expressive than the spread operator.

Library Usage

Neither of these approaches uses a specific library. They are built-in features of the JavaScript language.

Special JS Features/Syntax

There is no special JavaScript feature or syntax used in this benchmark. Both test cases use only standard JavaScript syntax.

Other Alternatives

If you need to merge objects, there are other alternatives:

• Array.prototype.reduce(): You can use reduce() to merge two objects.

const finalObject = firstObject.reduce((acc, key) => ({ ...acc, [key]: acc[key] }), {})

• JSON.merge() (ECMAScript 2022): This is a new method introduced in ECMAScript 2022 that allows you to merge two objects.

I hope this explanation helps!