Benchmark Overview

The MeasureThat.net benchmark tests the performance of three different approaches to merge objects in JavaScript:

1. The spread operator (...)
2. Object.assign()
3. Assigning properties dynamically using bracket notation (firstObject[secondObject[field]] = secondObject)

Spread Operator (...)

The spread operator is a new syntax introduced in ECMAScript 2018 (ES8). It allows you to expand an object into multiple arguments, making it easier to merge objects.

const finalObject = { ...firstObject, ...secondObject };

Pros:

• Concise and readable syntax
• Native support in modern browsers and Node.js environments

Cons:

• May have performance overhead due to the need for browser or engine optimizations
• Not all versions of JavaScript engines may implement it efficiently

Object.assign()

Object.assign() is a built-in method that allows you to merge multiple objects into one.

const finalObject = Object.assign(firstObject, secondObject);

Pros:

• Wide support across older browsers and Node.js environments
• Well-documented and widely understood by developers

Cons:

• Requires two arguments (target object and source object) in the most basic form, which can be less readable than the spread operator syntax.

Assigning Properties Dynamically

This approach uses bracket notation to assign properties dynamically.

firstObject[secondObject[field]] = secondObject;
const ob = firstObject;

Pros:

• Wide support across older browsers and Node.js environments
• Can be a good option when working with legacy codebases or specific browser versions

Cons:

• Less readable syntax compared to the spread operator or Object.assign()
• More error-prone due to potential typos in property names

Library: None

There are no libraries involved in this benchmark.

Special JavaScript Features/Syntax: ES8 Spread Operator

The benchmark uses the ES8 spread operator feature, which is a relatively new addition to the JavaScript standard. This feature allows for more concise object merging and has become widely adopted in modern JavaScript development.

Alternative Approaches

Other approaches to merge objects include:

• Using for...in loops to iterate over object properties
• Utilizing libraries like Lodash (_.merge())
• Employing custom function to merge objects based on specific requirements

However, the spread operator and Object.assign() methods are the most commonly used and efficient ways to merge objects in modern JavaScript development.