I'd be happy to help you understand the JavaScript microbenchmark on MeasureThat.net.

Overview

The benchmark compares three approaches for merging two objects:

1. _.merge() from Lodash
2. Object.assign()
3. The spread operator ({ ... })

Options Compared

• _._merge() from Lodash: A utility function that merges two or more objects into one, overriding properties with the same name.
• Object.assign(): A built-in JavaScript method that copies the values of all enumerable own properties from one or more source objects to a target object.
• The spread operator ({ ... }): A syntax feature in modern JavaScript that allows creating a new object by spreading the properties of an existing object.

Pros and Cons

1. _._merge() (Lodash):
   • Pros: Fast, efficient, and easy to use. Lodash is a popular utility library, and this function is well-maintained.
   • Cons: Requires importing Lodash, which may slow down the test.
2. Object.assign():
   • Pros: Built-in JavaScript method, fast, and widely supported.
   • Cons: May not be as intuitive or readable as other approaches.
3. Spread operator ({ ... }):
   • Pros: Simple, concise, and easy to read.
   • Cons: Only available in modern JavaScript environments (ECMAScript 2018+).

Library and Syntax

The benchmark uses the Lodash library for the _._merge() function.

Note that the spread operator is a syntax feature introduced in ECMAScript 2018. If you're using an older version of JavaScript, this approach won't work.

Test Case Breakdown

Each test case defines a simple scenario:

1. Two objects a and b with some properties.
2. A new object c is created by merging a and b.

The benchmark measures the execution time for each approach to create c. The raw UA string, browser version, device platform, operating system, executions per second, and test name are all provided.

Other Alternatives

Other approaches for merging objects could include:

• Using the Object.create() method and setting properties.
• Utilizing a custom merge function or algorithm.
• Leveraging other libraries like merge-deep or deep-merge.

However, these alternatives are not tested in this specific benchmark.