The provided JSON represents two benchmark test cases for JavaScript microbenchmarks on MeasureThat.net. Let's break down what each part of the JSON represents and explain the test cases.

Benchmark Definition

The benchmark definition is represented by the top-level object containing information about the benchmark, such as its name, description, script preparation code, and HTML preparation code (which is empty in this case).

Script Preparation Code

The script preparation code defines a custom JavaScript function called cloneDeep that creates a deep copy of an object. This function handles various cases, including:

• Dates: it creates a new Date instance with the same timestamp.
• Arrays: it recursively clones each element in the array.
• Objects: it recursively clones each property in the object.

This suggests that the benchmark is testing the performance of two ways to create copies of objects in JavaScript: using the spread operator (...) and a custom cloneDeep function.

Test Cases

The test cases are represented by an array of individual objects, each containing information about a specific test case:

• The first test case uses the spread operator (...) to create a copy of an object.

const car = {type:"Fiat", model:"500", color:"white"};
let carCopy = {...car, type:"Ford"};

This creates a shallow copy of the car object, only updating the type property.

• The second test case uses the custom cloneDeep function to create a deep copy of an object.

const car = {type:"Fiat", model:"500", color:"white"};
let carCopy = cloneDeep(car);
carCopy.type = "Ford";

This creates a deep copy of the car object, including all its nested properties.

Benchmark Results

The latest benchmark results are represented by an array of objects, each containing information about a specific test case:

• The first result is for the test case using the spread operator.

{
  "RawUAString": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36",
  "Browser": "Chrome 102",
  "DevicePlatform": "Desktop",
  "OperatingSystem": "Windows",
  "ExecutionsPerSecond": 54393304.0,
  "TestName": "Using the spread operator"
}

This result shows that the test case using the spread operator executed approximately 54 million times per second.

• The second result is for the test case using the custom cloneDeep function.

{
  "RawUAString": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/102.0.0.0 Safari/537.36",
  "Browser": "Chrome 102",
  "DevicePlatform": "Desktop",
  "OperatingSystem": "Windows",
  "ExecutionsPerSecond": 1477223.375,
  "TestName": "Using cloneDeep"
}

This result shows that the test case using the custom cloneDeep function executed approximately 1.5 million times per second.

Alternatives

Other alternatives for creating copies of objects in JavaScript include:

• The built-in Object.assign() method, which creates a shallow copy of an object.
• The JSON.parse(JSON.stringify(obj)) trick, which creates a deep copy of an object by serializing it to JSON and then parsing it back.

However, these methods may not be as efficient or accurate as the custom cloneDeep function in certain cases.