Let's break down the provided benchmark definition and test cases to understand what is being tested.

Benchmark Definition

The benchmark measures the performance of two approaches for iterating over an array:

1. $.each(arr, function(key, val) { ... }); - This uses jQuery's $.each() method.
2. Object.keys(arr).forEach(function(key) { ... }); - This uses the Array.prototype.forEach() method.

Script Preparation Code

The script preparation code creates an array arr with four elements: aa, bb, cc, and dd.

Html Preparation Code

The HTML preparation code includes a reference to jQuery version 3.3.1, which is used by the benchmark.

Test Cases

There are two test cases:

1. jQuery.each: This test case uses the $.each() method from jQuery to iterate over the array. The script prepares a temporary variable temp and assigns it the value of each element in the array.
2. Array.prototype.forEach: This test case uses the forEach() method on the Object.keys() result of the array, which returns an array of keys. The script prepares a temporary variable temp and assigns it the value of the current key (which is actually a string representation of the index).

Library

In both test cases, jQuery's $.each() method is used as a reference implementation for iteration.

Special JavaScript Feature or Syntax

There are no special features or syntaxes used in this benchmark.

Pros and Cons

Here are some pros and cons of each approach:

• $.each(): Pros:
  • Easy to use, especially for those familiar with jQuery.
  • Can be more concise than other approaches.
• Cons:
  • jQuery is a large library that adds overhead.
  • The method is not part of the standard JavaScript API.
• Array.prototype.forEach(): Pros:
  • Part of the standard JavaScript API, so no additional libraries are needed.
  • More efficient than $.each() in terms of performance.
• Cons:
  • Can be less intuitive for those unfamiliar with the method.
  • May require more code to achieve the same result.

Other Alternatives

Some other alternatives for iterating over arrays in JavaScript include:

1. for...of loop: A modern and concise way to iterate over arrays using a for...of loop.
2. map(), filter(), and reduce() methods: While not as straightforward as forEach(), these methods can be used for more complex operations on array elements.

In the context of this benchmark, the use of $.each() versus Array.prototype.forEach() is primarily a matter of syntax choice and familiarity. The test results will likely show that Array.prototype.forEach() outperforms $.each() due to its native implementation in JavaScript.