Overview

The provided JSON represents a JavaScript microbenchmark test case on MeasureThat.net. The benchmark tests the performance of three different approaches for merging two objects in JavaScript: using the spread operator, Object.assign, and creating a new object with Object.assign. The test results are compared across various browsers and devices.

Benchmarked Approaches

1. Using the spread operator: This approach uses the syntax {...obj1, ...obj2} to merge two objects, obj1 and obj2. The spread operator is a shorthand way of creating a new object with properties from multiple sources.
2. Object.assign (existing): This approach uses the traditional Object.assign() method to merge two objects. It assumes that both inputs are objects and attempts to assign all own enumerable property values of one or more source objects to an existing target object.
3. Object.assign (new object): This approach creates a new object using Object.assign({}, obj1, obj2) and then assigns the result to the new object.

Comparison

The pros and cons of each approach are:

• Using the spread operator: Pros:
  • Concise syntax
  • Easy to read and write
  • No need to create a new object explicitly Cons:
  • May be slower than traditional Object.assign() due to the overhead of creating a new object
  • Not supported in older browsers (e.g., IE 8-10)
• Object.assign (existing): Pros:
  • Faster execution compared to the spread operator
  • Supported by most modern browsers Cons:
  • Requires explicit creation of an object using new Object()
  • May lead to unexpected behavior if not used carefully (e.g., merging arrays with objects)
• Object.assign (new object): Pros:
  • Similar performance to traditional Object.assign()
  • No need to worry about creating a new object explicitly Cons:
  • Creates an extra layer of nesting, which may be confusing for some developers

Library and Features

The benchmark does not use any external libraries. However, it does utilize JavaScript features such as:

• Spread operator ({...obj1, ...obj2})
• Object.assign() method

These features are supported by most modern browsers.

Test Results

The latest test results show that:

• Using the spread operator has the slowest execution time (3138294.75 executions/second) compared to traditional Object.assign().
• Creating a new object with Object.assign({}, obj1, obj2) has a similar performance to traditional Object.assign().

Alternatives

Other alternatives for merging two objects in JavaScript include:

• Using the {...obj1, ...obj2} syntax with Object.create() (e.g., const finalObj = Object.create(obj1); finalObj[Symbol.for('foo')]= obj2['foo']; )
• Using a library like Lodash's merge() function
• Creating an array of properties and then using Object.assign() to merge the objects

However, these alternatives may introduce additional overhead or complexity compared to the traditional approaches tested in this benchmark.