Let's break down the provided benchmark and its test cases.

Benchmark Overview

The benchmark measures the performance of shallow copy operations on an array. The input data is fetched from a JSON endpoint using the fetch API, which returns a JSON response. This response is then assigned to the data variable. The goal is to create a shallow copy of this data and compare the performance of different methods.

Script Preparation Code

The script preparation code fetches data from the specified JSON endpoint using the fetch API:

var data = [];
var res = [];

fetch('https://jsonplaceholder.typicode.com/posts')
  .then(response => response.json())
  .then(json => data = json);

This code uses the fetch API to make a GET request to the specified endpoint, which returns a JSON response. The response is then parsed as JSON and assigned to the data variable.

Html Preparation Code

There is no HTML preparation code provided for this benchmark.

Test Cases

The test cases are defined in the individual test cases array:

[
  {
    "Benchmark Definition": "res = data.slice();",
    "Test Name": "slice"
  },
  {
    "Benchmark Definition": "res = data.concat();",
    "Test Name": "concat"
  },
  {
    "Benchmark Definition": "res = [];\r\ndata.forEach(element => res.push(element));",
    "Test Name": "forEach"
  },
  {
    "Benchmark Definition": "res = [];\r\nfor (let i = 0; i < data.length; i++) {\r\n\tres.push(data[i]);\r\n}",
    "Test Name": "Traditional For Loop"
  }
]

Each test case defines a different method for creating a shallow copy of the data array:

• slice: Creates a shallow copy of the entire data array using the slice() method.
• concat: Creates a new array by concatenating all elements from the data array using the concat() method.
• forEach: Creates a new array by iterating over each element in the data array and pushing it to a new array using the forEach() method.
• Traditional For Loop: Creates a new array by iterating over each element in the data array using a traditional for loop and pushing it to a new array.

Library: None

There is no library used in this benchmark. The only library mentioned is fetch, which is part of the browser's native API.

Special JS Feature or Syntax: None

There are no special JavaScript features or syntax used in this benchmark.

Benchmark Results

The latest benchmark results show the performance of each test case:

These results indicate that the traditional for loop method is the fastest, followed closely by the slice() method. The forEach() method and the concat() method are slower.

Other Alternatives

If you're interested in exploring alternative shallow copy methods, here are a few options:

• Array.prototype.map(): Creates a new array with the result of applying a provided function to each element in this array.
• Array.prototype.reduce(): Applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

These alternatives can be used to create shallow copies, but they may have different performance characteristics compared to the methods tested in this benchmark.